Hmmm, ok, I've got to confess I've never read the 3E description. Is that the first time it appears? It doesn't seem to match any actual named phylacteries that appeared over the years.
EDIT: I found
this post which says they didn't start to resemble tefflins until 3E, but the change may have been presaged by Van Richten's Guide to the Lich. So looks like some author started conflating them late in 2E, and that got carried over. Can't blame this one on Gygax...
EDIT2: Checking Van Richten's guide, it calls it a "usually a box-shaped amulet", (but not always) but doesn't say anything about paper inside.... looks like that bit got added in 3E.
So it seems to problem isn't the name, but how they suddenly changed to a very specific thing in 3E.