I have a Birdy III with the H&H front block adapter and it didn't move down, even with the front bag heavily loaded.

Yes, please publish the video if you can or send me a message with a link to i if you cannot.

For the easy wheel, when i wrote "Brompton easy wheel" I was meaning any easy wheel for Brompton with a M6 bolt, not made/sold by Brompton.

The only limitation is if you want to put a rear pannier on the rear rack and have relatively big feet. Then to avoid to hit the pannier with the heels, you need to put the pannier very much to the rear, and easy wheels above 45mm in diameter do not allow to put the pannier at the rear end of the rear expedition rack.