The 250 knot speed limit is below 10,000’ msl. Now it’s true that most Class B sits within this restriction, but the Bravo is not what’s generating the limit. It’s a minor distinction, but here’s a practical example from just last night: landing SLC to the north on the QUENN 5 arrival, and I was descended by ATC to 10,000’. The ceiling of the Bravo is 12,000’, and I was already well within the lateral boundary. We were running late and I really had to pee. How fast do you suppose I was going?