Yeah, this is either purely political (i.e. somebody probably told him "This could help you with younger voters!") or pardoning him would just be his unsophisticated middle finger at the IC, since they don't like Snowden & he's pissed off with them for not backing down on the fact that Russia is interfering with elections to help him win (presumably, his child-like, zero-sum brain thinks that this would hurt them, & they're his enemy, so this means winning).
in context, I think its more he has completely forgotten who Snowden is and gave his standard response when he doesn't know something (BS a confident yet vague response). He gave exactly the same reply when somebody asked him if he was going to pardon Joe Exotic.
I think you've hit the proverbial nail on the head here.
If we had a real press corps, they would have followed this up with "Could you please explain who Edward Snowden is and what he did?" And then when he tries to give one of his patented 'didn't do his homework' answers, keep pushing him until he flees. If they'd done this in 2015, he wouldn't be in the White House, and a 100,000 more Americans would be alive. If they'd done it for the last four years, we wouldn't have to worry about him remaining in office.
