I forgot to mention most of the concern for why ATF is an excellent cleaning agent.
Again back to the high detergent package in the oil. Back in the day BMW had likely one of the worst transmissions across the range. The ZF 4HP 22/24/EH.
The transmissions had many flaws internally; from bad stator seals. F clutch drums that had hard steel snap rings riding on aluminum drums, A clutches that wouldn't drain and would melt the clutches/steels if revved in neutral etc.
So performing due diligence one drops the pan, changes the filter/fluid and the detergents went to work, cleaning up all of the debris in/around the aforementioned areas. The trans would stop working within a week or less.
This is EXACTLY where all of the theories of "Do not change the automatic transmission fluid on BMW's" came about. It still persists to this day.
We've had VG luck with the day before regimen. If it's worked for you, go for it.
BTW, the newer ZF 6 & 8 speed transmissions are proving to be very robust. Only the 6 speed has issues with valve body to trans seals hardening. Change them with normal service (ZF recommends 100Km) and all is good.