I still haven't seen anything which says a controller isn't allowed to do it. And it certainly isn't a "misapplication of Part 91" if the pilot does exactly what the regulation says.
FAA ORDER JO 7110.65U Air Traffic Control
Chapter 7. Visual
Section 7. Terminal Radar Service
Area (TRSA)− Terminal
7−7−5. ALTITUDE ASSIGNMENTS
a. Altitude information contained in a clearance,
instruction, or advisory to VFR aircraft must meet
MVA, MSA, or minimum IFR altitude criteria.
REFERENCE−
FAAO JO 7110.65, Para 4−5−2, Flight Direction.
FAAO JO 7110.65, Para 4−5−3, Exceptions.
FAAO JO 7110.65, Para 4−5−6, Minimum En Route Altitudes.
b. If required, issue altitude assignments, consistent
with the provisions of 14 CFR Section 91.119.
NOTE−
The MSAs are:
1. Over congested areas, an altitude at least 1,000 feet
above the highest obstacle; and
2. Over other than congested areas, an altitude at least
500 feet above the surface.
c. When necessary to assign an altitude for
separation purposes to VFR aircraft contrary to
14 CFR Section 91.159, advise the aircraft to resume
altitudes appropriate for the direction of flight when
the altitude assignment is no longer needed for
separation or when leaving the TRSA.
PHRASEOLOGY−
RESUME APPROPRIATE VFR ALTITUDES.
REFERENCE−
FAAO JO 7110.65, Para 4−8−11, Practice Approaches.
FAAO JO 7110.65, Para 5−6−1, Application.
FAAO JO 7110.65, Para 7−2−1, Visual Separation.
Section 8. Class C Service− Terminal
7−8−5. ALTITUDE ASSIGNMENTS
a. When necessary to assign altitudes to VFR
aircraft, assign altitudes that meet the MVA, MSA, or
minimum IFR altitude criteria.
b. Aircraft assigned altitudes which are contrary to
14 CFR Section 91.159 must be advised to resume
altitudes appropriate for the direction of flight when
the altitude is no longer needed for separation, when
leaving the outer area, or when terminating Class C
service.
PHRASEOLOGY−
RESUME APPROPRIATE VFR ALTITUDES.
REFERENCE−
FAAO JO 7110.65, Para 7−2−1, Visual Separation.
Section 9. Class B Service Area− Terminal
7−9−7. ALTITUDE ASSIGNMENTS
a. Altitude information contained in a clearance,
instruction, or advisory to VFR aircraft must meet
MVA, MSA, or minimum IFR altitude criteria.
b. Issue altitude assignments, if required, consistent
with the provisions of 14 CFR Section 91.119.
NOTE−
The MSAs are:
1. Over congested areas, an altitude at least 1,000 feet
above the highest obstacle,
2. Over other than congested areas, an altitude at least
500 feet above the surface.
REFERENCE−
FAAO JO 7110.65, Para 4−5−2, Flight Direction.
FAAO JO 7110.65, Para 4−5−3, Exceptions.
FAAO JO 7110.65, Para 4−5−6, Minimum En Route Altitudes.
c. Aircraft assigned altitudes which are contrary to
14 CFR Section 91.159 must be advised to resume
altitudes appropriate for the direction of flight when
the altitude assignment is no longer required or when
leaving Class B airspace.
PHRASEOLOGY−
RESUME APPROPRIATE VFR ALTITUDES.
Prior to the establishment of TCAs, what we now call Class B airspace, around 1970,
there was no provision in FAR 91.159 (then FAR 91.109) for ATC authorization of
incorrect VFR cruise altitudes. Here is the old regulation:
91.109 VFR cruising altitude or flight level.
Except while holding in a holding pattern of 2 minutes or less, or while
turning, each person operating an aircraft under VFR in level cruising flight
more than 3,000 feet above the surface shall maintain the appropriate altitude
or flight level prescribed below:
(a) When operating below 18,000 feet MSL and--
(1) On a magnetic course of zero degrees through 179 degrees, any odd
thousand foot MSL altitude +500 feet (such as 3,500, 5,500, or 7,500); or
(2) On a magnetic course of 180 degrees through 359 degrees, any even
thousand foot MSL altitude +500 feet (such as 4,500, 6,500, or 8,500).
(b) When operating above 18,000 feet MSL to flight level 290 (inclusive)
and--
(1) On a magnetic course of zero degrees through 179 degrees, any odd
flight level +500 feet (such as 195, 215, or 235); or
(2) On a magnetic course of 180 degrees through 359 degrees, any even
flight level +500 feet (such as 185, 205, or 225).
(c) When operating above flight level 290 and--
(1) On a magnetic course of zero degrees through 179 degrees, any flight
level, at 4,000-foot intervals, beginning at and including flight level 300
(such as flight level 300, 340, or 380); or
(2) On a magnetic course of 180 degrees through 359 degrees, any flight
level, at 4,000-foot intervals, beginning at and including flight level 320
(such as flight level 320, 360, or 400).
If ATC was to provide separation for VFR aircraft it must have authority to
assign routes, altitudes, and headings to VFR aircraft and the FAR had to
be changed or pilots could be in violation when complying with ATC instructions.
But enough of this. Mr. McNicholl is incorrect on this point as far as a pilot and Part 91 are concerned no matter what he thinks a controller is or is not permitted to do, and that is black letter law.
As you understand it, but your input in this forum often indicates a disparity between what is written and your understanding of it.