I'm guessing the reviewers in question aren't familiar enough with
NSTimer (or possibly even Objective-C) to determine if that is indeed correct or altering the answer and behaviour of the code.
It's pretty hard to work that out quickly for things you're not familiar with. For edits like that (as opposed to grammatical/spelling/formatting edits) I would normally pass over them and defer to someone who (hopefully) has more experience in the tags.
The obvious "fix" that springs to mind would be requiring a minimum amount of rep in a tag in order to approve edits, but the problem there seems to be that it would significantly reduce the pool of people eligible to review (which is bad for the simpler to judge edits).
To work around that there could be an option when submitting an edit to require reviewers have tag relevant experience. I don't think that would work well in practice though because it might end up being abused. One solution might be to make that automatic based on editing the content of code blocks - you'd want to avoid whitespace counting for that, although that in itself might be problematic for at least Python.
The other option (beyond simply resubmitting and hoping you get different reviewers) would be a flag option on the suggested edit page itself. Under the hood this could be just window dressing on the existing flagging mechanism and raise an "other" flag on the answer in question pre-filled with a link to the edit. There's a penalty there for abuse (loss of flag weight) and "oversight" from higher up the chain. Alternatively the flag this suggested edit might move the edit back into another "require tag experts to review" queue.
Both of those seem like a lot of work to implement though over the existing options (flag answer or resubmit edit) and it's quite an edge case too so I doubt they'll happen.