That is the current incarnation of parchment paper, but before that it was impregnated with Quilon, which I understand is fatty acids stabilized with trivalent chromium.
The concern is twofold. First, chromium is an element and as such does not break down, it can only be secreted. Second, the higher oxidation state Cr(VI) is a known carcinogen. It's claimed the Cr(III) here will not oxidize to Cr(VI) under normal cooking conditions, however.
My understanding is the claim that Cr is a necessary micronutrient is disputed.
so... wholly unrelated to the claim that it's impossible to make parchment paper without polyfluoroalkyl substances which is what was being refuted in the thing you replied to?
A cool thing about silicones is they complicate the processing of landfill gas. That gas is from bacterial decomposition of waste landfills, and is mostly methane + CO2. So burning it in small engines or turbines makes sense. But it also has silicon-bearing volatile compounds from decomposition of silicones, and if you burn those in an engine you fill it with particles of silica, which abrade surfaces and form glassy coatings on turbine blades.
An additional source of silicones in landfills is cosmetics, of which they form a substantial fraction.
There are valid uses for silicone, for example high quality silicone gaskets for leak proof containers are a very solid use case. We should just not use it for everything that's remotely applicable.