The only thing that doesn't make me so sure is that if you bolt a 2/3 tarmogoyf (with no instants in the yard) it becomes 3/4 before it dies and thus survives. I am wondering if the same applies to players. The only difference I could see is that Ascension is a trigger whereas tarm's P/T is a state-based check.
The difference is as you note. After the spell finishes resolving, the Goyf would be a 3/4, and SBE's are checked after full resolution of a spell (which includes going through/to the appropriate zones).