I did my "complex" signoff long before the rules required one - but the club wasn't about to let me off into the blue yonder in a 140 knot C177RG, when up to then I'd been flying Rallyes, C152s, and PA28-140s - none of which came close to 100 knots.
I had about two hours with the CFI, of which maybe 15 minutes was about gear, prop and cowl flaps. The rest was learning to stay ahead of a much faster aeroplane.
I could see the sense in that. I can't see anyone who's used to the speed of the "complex" type needing more than an hour at most to learn the wheels and prop bit.