I might have said "maybe they're saving them for something", but considering how little we got with Shadowbringers, I think that reasoning is flawed.

In all likelihood, the reason is probably just that WHM doesn't have any Water magic (because as a healer, they don't need more than the bare basics of an attack rotation) so giving us the Ver- iteration of a spell that doesn't exist would be jarring, and giving us Blizzard without something to balance it would defeat the job's aesthetic.

Or something. We all know if they wanted to they could just skip past that entirely. They could even justify having RDM copy spells from other casters. Not like they have an explanation for why SMN can call on a secret Demi-Primal that was an optional boss.