That may be the target, but there have been a handful of Spelling Bees with less than 20 words in the answer list. For instance, March 27, 2023 had 16 answers:
> MORTIFY, FORTIFY, FIFTY, FORTY, MOTIF, FIRM, FOOT, FORM, FORT, FROM, IFFY, MIFF, RIFF, RIFT, ROOF, TIFF