One of my cars has more bubbles than that on rear window. I asked and received the same answer.. It might damage the rear demister too.. They can't guarantee it.. 50/50

So I decided to leave it instead..

Not so true. The film can be removed without damaging the heating elements.

Just that you will be informed beforehand that there's no guarantee it won't be.

When there's bubbles, it shows that the film is peeling off on its own. One installer I went to, uses a heat gun. No damages to heating elements at all.

Another thing, the installer said that the old tinted film is among the better quality ones and easier to peel off in one piece without tearing. That helps too.