We've looked more into how Trades are handled with downleveling once you trade to low level accounts, and have verified that the minimum is indeed 20, rather than 15. A misunderstanding from a few months ago is the cause.
PGET has been updated to handle this and it'll be revised with the next stable release of PKHeX.
PKHeX uses the 3DS's wordfilter, as it's the strictest one documented (and the only one documented, at that).
https://www.urbandictionary.com/define.php?term=SOB