I experimented with width and height a lot to see if those properties affected the format property. Keeping in mind that width is under Bounds and height is under Common, changing either width or height didn’t seem to make a difference. The “300x250” is the only format selection that seems to have this problem. I get a control that is only 50px wide.
It seems: When format “300x250” is selected, a width of “50” is being passed to the underlying code instead of “250”. If I were to guess: It’s as if the underlying code has a copy/paste error from the “320x50” selection.
FWIW, I was (also) not able to get your hosted example (https://adsense-wets-correctly.volt.live/) to work for me, but I only spent a limited amount of time trying to make sure I had ad blockers turned off (along with all the related settings that could be in the way). But it might be worth a once-over, in light of “It’s been a long time since we revisited this sample”.