"Looking at some website, it appears their are two different flavours
of
240V GFCI breakers. 1 supports the 120/240 mix, and one is strictly
only 240. Looks like my electrician gave me the wrong one. "

That's exactly the conclusion I just came to also! At least it's easy
to fix. The electrician should switch it and only charge you the price
difference. Sounds like he wasn't familiar with spas, as all the ones
I've seen need both 240 and 120V.