It's possible they stick him on the roster day 1 to open up next year. If they do that it will look kinda dumb that they didn't bring him up this year. Although I do agree they should just wait until they get the extra year of control next year.
I’d give Grandal the next couple of weeks to show some life. I’d rather not carry a third catcher with one of those 2 call ups and would rather add 2 players + Perez while ILing Grandal like you said.