For some reason, I get the opposite effect. I feel that the resulting brew from my plastic Aeropress loses more heat than my glass french press, so I have to preheat my coffee mug if I’m using my AP.

Giving it some thought, the effect may not be the AP material itself, but the heat loss from the high surface to volume ratio of the droplets as they come out of the filter, as opposed to the stream as the liquid is poured out in a single thick stream out of the french press.

i.e. A glass Aeropress may not reduce temperature loss significantly over plastic.

But my desire for a glass Aeropress is more for reducing plastic use, and risk of shedding microplastics into foods that I consume.