That would be pair programming with extra steps if you're just reviewing updates and not the whole patch that is going to be merged (and which is stamped with your approval).
Not sure if it's just my age but pair programming seems to have a different meaning these days.
It used to mean that two developers would literally sit next to each other, one would type and one would review as the person typed, then they would repeat.
I guess in the world of remote working it's just not practical any more.
I certainly wouldn't call, one person reviewing another persons code during the merge process pair programming at all.
Junior dev working on feature X
Junior dev makes a lot of commits and creates PR
Senior dev reviews code, spots problems a,b,c but has reviewed all the code at this point. Feature X isn't complete it can't be merged
Junior dev fixed a,b,c now 90% of the already reviewed code might not have changed but the PR doesn't show that.
Now replace junior dev with agent.