Funny Spell Check issue

I recently installed 8.5.1 FP5 and it’s spell checker seems to have improved over FP3 or FP4. I’ve seen spell check do some weird things over the years, but this one topped all.

I had typed a phone number into the body of an email, standard (555)555-5555 format. Spell check said it was spelled incorrectly. It didn’t have any suggestions, but none the less it popped up. The auto spell check didn’t have it underlined, but the on send spell check reported it. Has anyone else seen this happen?

To test, create a new message, type in (555)555-5555, then Tools, Spell Check.

I tested the same thing on a windows machine running 8.5.1 FP5 and it doesn’t do this. It’s only happening on the Mac.