We don’t get much spam but I just did “Agree and delete user” on a particularly egregious piece of spam. The response was an error worded something like in the title:
You are not permitted to view this resource.
(Sorry, didn’t think to take screenshots.)
I assume this was a default response to an automatic refresh of now-deleted content. I would have expected a more graceful success message.
The error message that you received is not the response that is expected when you select the “Agree and delete” user option from the review queue. I will see if I can find a way of duplicating that error on my site.