Yeah, that's a standard of canonicity that's hard to apply to a series like Sailor Moon, where half the episodes are completely inconsequential. I really don't see the point in being so restrictive.I hate to say it, but by that standard, some of these TV episodes may not be canonical…
Apart from the SuperS movie (whose continuity errors wreak havoc on the main series' plot), it's not much different from, say, the Doom Tree arc : inoffensive filler. Heck, the S movie is a nearly direct adaptation of a short manga arc, which is more than most episodes can claim.
(And I say this as someone who doesn't even really like those movies much.)