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I was using water from my RO filter and still am. I noticed it with other ice trays at other locations, but thought it was just something that happened to ice sitting in the freezer rather than coming from the ice tray itself, until I got one of those silicone sphere ice trays that only has a tiny bit exposed and noticed it was worse instead of better. It was also my first non-white ice tray, and I could clearly see the white film that remained on the silicone, which prompted me to buy the metal tray.

Fridge ice makers probably aren't an issue because the ice doesn't sit in the tray for very long (which also might be metal). They can sit in a plastic tub for a while before being dispensed, but they don't have full contact with that plastic, and ice in the middle wouldn't even have any contact until ice shifts around.

I wouldn't be surprised if it depends on the type of plastic the tray is made out of, too. Like the silicone being worse might have been due to the plastic itself as much as the higher amount of contact with the ice.

And even without that, the metal one is just nicer to use. It is a normal tray with a metal grid attached to a hinged handle that easily breaks the ice. I've had a plastic tray partially snap while trying to twist the ice out, though even when they didn't break, the ice would also sometimes refuse to break free.