[nynyny7]

As for "there seem to be quite a few different Atari 1040ST board designs" noted in the article. There is actually a huge number of different board layouts. Look at the entries for "STF" or "STFM" in this overview: https://temlib.org/AtariForumWiki/index.php/Atari_ST_motherb....

As for why Atari redesigned the board so many times: no idea.

[cmrdporcupine]

Seemed common back then. Esp for the Tramiels. There's so many different C64 boards, for example. Likely for cost savings in manufacturing.