Hmm, I’ve often wondered this – would happily use my planet x superlight carbon pro on my turbo trainer, as I reckon that is strong enough. When I have used it in there it hasn’t flexed unduly. If I was really cranking it (unlikely being as it’s me) then I would be a little bit more sceptical, and have noted it flex significantly more than on the road. This is because on the road, the bike would lean with my body weight but it can’t when clamped in putting a lateral load on the dropouts.
However, my BMC pro machine would go nowhere near it, as I’m not planning on mullering a £2400 frame on it.