Not quite sure how this helps.
The rule is any Dex save fails (regardless of the source) when you are paralysed. Get hit by a fireball spell, fail your save. (And I
so need to do that more in my D&D games).
So, even when you're saving against poison and not paralysis, because it's a Dex save you fail.
I really like how their wording that makes it poison that paralyses; really awesome stuff. And there a few poison instances in the MM that last an hour with no save ends (LOVE IT!)
Just this one they fell into the trap of Dex and Str saves being actually surprisingly dangerous to use as ongoing saves. (That's not a new rule, either!)
Cheers!