I thought of this too and then laughed, but…
I can kind of.. sort of… see a way where this is a response to the last-minute rule change from the NFL. “Oh we can’t have a PS QB be our number 2 and our guy on the 53 be our emergency freebie number 3? Well, we’ll just make one guy ‘exempt’ and then have the other guy take his temporary roster spot until he’s ready…”
That said, Corral being exempt means he won’t be practicing so I really doubt this is the case, but it’s so bizarre that it makes me suspicious lol