I think you're checking a different reference than he had in mind...
https://en.wikipedia.org/wiki/Tefillin
I think he's just saying that in 1e this was assumed by common knowledge of the meaning of the word "phylactery."
In 2e, the phylactery is explicitly stated to often be hidden away. If not stated in this way, "phylactery" is a word with a known meaning.
Sort of like if it said the Lich maintains his status by "certain conjurations, enchantments, and a sexy nose piercing." The assumption would be, barring any other statement, that the nose piercing was actually present in the Lich's nose.