yes, it will change some of the "shared" bits, like the plugin manager, if that counts as "interfering" - no idea what the impact might be

Installed the Platinum trial a couple years ago. Then after uninstalling the trial, I had to re-install all of my Sonars (8.5-X3) for some reason.  I think it messed up my Cakewalk plugins...

I think they are maybe looking for a different kind of trial.  Maybe a self flagellation / hair shirt kind of thing ?
 
JR

Personally I wouldn't try it on my main DAW because of potential screw ups. Example I already have Cubase Elements & and I downloaded the free trial of the latest full version which was at the time Cubase 8. I later uninstalled it after a week or so. 
 
Next time I opened Wave Lab my e licencer was messed up now. I fixed it. Then I opened Cubase El 7 and it was messed up. ?? so I had to re installed it. So demos are to approached with caution. 
 
And really whats the point of trying something you can't buy? That's why I mentioned Home Studio which is free and it will give you most of what the demo had anyhow. And it will be yours to keep.