this is not how we handle crossovers, there are countless verses that are "Canon!!!!" to other verses. In a significant enough context you could argue to merge the pages. Without that significant enough context (Cory Balrog saying "totes canon" is not that, for sure), you can't. The God of War shit for Shovel Knight isn't even on every platform the game features in lmao, they aren't owned and written by the same entities. This is lower on the scale of crossover priority than shit like Mr. X from Resident Evil appearing in Monster Hunter.
Crossovers are canon to an extent, but without substantial support in every single department, this shit doesn't fly on the wiki. I'd list myself under the "not canon" option in the OP as that most closely resembles my thoughts on the matter, but Lephyr is also correct in that it would almost certainly still be an outlier for the Shovel Knight to have one (1) 2-C feat of fighting Kratos and then never have anything again, in a currently rather expansive series of games.
TL;DR: Crossover rules say no, even if they didn't this disregards all logic concerning outliers.