I always head straight here:
https://www.caa.co.uk/drones/getting-started-with-drones-and-model-aircraft/drone-code/updates/#
Any major, minor or planned changes clearly stated.
I think the real point is that this isn't something that is made plain to prospective purchasers... I was one of those people that threw a blue-arsed fit when DJI released that firmware for the mini 3 pro that hobbled the max altitude to 400'...
...and because it's now in a heavier weight class: as pointed out by Gadgetguy, you don't have the freedom to fly in any of the places a sub-250grm drone can under the A1 sub-category, you also are now limited to flying in accordance with A3...