I think that directly depends on the rigor or the reviwers. If people at least follow the instructions in PRs already reviewed, i.e. actually run nix-review and fix the issues it reports, even if it is just marking packages as broken, it is a net positive. If they don’t, merging new PRs will probably break things.
Regarding the concerns of incentivizing wrong things: Its always a risk with gamification. However I think this is harmless here. I see nothing wrong with nitpicks as long as they have at least a little merit. Nothing wrong with a high standard. Gaming merges/approvals without proper review will get noticed by the community in the long run.