Two sections of the AIM address reporting entering a hold.
5-3-3
Additional Reports
a. The following reports should be made to ATC or FSS facilities without a specific ATC request:
1. At all times.
(f)The time and altitude or flight level upon reaching a holding fix or point to which cleared
5-3-8
Holding
f. Pilots should report to ATC the time and altitude/flight level at which the aircraft reaches the clearance limit and report leaving the clearance limit.
First, these reports are not restricted to when not in radar contact so that doesn't matter. One reason why reports in holding can be important, even in radar contact, is if there are multiple aircraft in the hold the data blocks can overlap making it more difficult for ATC to see the information.
Second, the wording between the two paragraphs is slightly different. One says "
clearance limit" while the other says "
holding fix". The hold on the ODP is a holding fix but it is not a clearance limit.
I think that, because the holding fix is not a clearance limit, ATC will be less likely to need the report. However, it is still a holding fix so I'll make the report anyway. That way I'm covered no matter what he wants or is expecting.