It probably just depends upon the reviewer.

For exclusives, the irrelevant keywords are removed upon inspection.
For non-exclusives, there is supposed to be a rejection for poor keywords. If there's nothing else wrong with the image, it can be resubmitted. There have been reported cases where a kind inspector has removed the poor keywords and accepted the file.
If you had ever tried to demonstrate iStock to a potential buyer, and the search results were so bad (because of poor keywording) that not only did he burst out laughing, but also called his colleagues over for a laugh, you'd think bad keywording was a serious issue too.
Even now, I see badly keyworded files being accepted day and daily.    My wiki finger is worn to the bone, and that's only within a very narrow field of interest.

If you're non exclusive it depends how many irrelevant keywords you have on a submission. If it's only a few, then the inspector will remove them for you and accept the image (assuming there are no technical issues with the image). The words that were removed are detailed on your acceptance email.

If there are lots of bad keywords then they won't do it for you and will reject your image with a note to advise which keywords you should remove for your re-submission.

I have had both experiences - image rejected for one or two keywords, and image accepted with keywords removed.

I very much appreciate the inspectors who are nice enough to remove the words and accept the image, but I understand they are not required to do that.