Not mistakenly at all: There is a (definitely valid): "Edit is too minor" rejection reason:

> This edit is too minor; suggested edits should be substantive improvements addressing multiple issues in the post.
 
There is a good reason for this. *Allowing small edits would clog the edit queue*. Moreover, you earn reputation and a badge for suggested edits, we expect people to put some effort into editing.

A spelling mistake is not going to prevent people from answering the question, so it's *just a spelling mistake*. Unless the editor improved the post significantly, such edits should definitely be rejected as too minor.