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.
