I don't think that's true at all.
I had a ClearCal on my old pro and it worked great.
The whites were a little prismatic, so they were somewhat colorful (like when a raindrop fell on your screen, though not nearly that dramatic). It was barely noticeable, I only saw it when I was looking for it on a very white screen. It's minimal.
The only problem is applying it without dust. I did it in my car where I had just vacuumed because I have dogs and live in a home under construction, but if you can get it done somewhere relatively low on dust (Even try somewhere like a public library where it's really rather clean, it's not a loud or long process), it'll be fine.
Then you can take it off with a simple piece of tape and reapply if you really want to. No residue.