Wouldn't the real problem be other things leaking back in? If the helium just leaves, that's a vacuum. If only helium can pass, then it's going to stay helium in there.
In this particular case I see it as a planned deprecation, sort of.
It would be a disconcertingly new phenomenon to find every drive in some old archival NAS failed simultaneously, or every one In a collection of external drives, because all drives last exactly 5 years with little variation, even when switched off, due to helium loss.