The official policy for bikes on the french high-speed trains is the following: compactify your bike so that it fits in a bag with size smaller than 90 x 120 cm (nothing is said about the thickness, nor whether e.g. the wheels of your bike must fit in the same bag or are allowed to stand next to the bag). In that case, your bike is allowed on board and rides for free.
On some TGV trains -the ones with a bike icon next to them when you make an online reservation- bikes are allowed in larger formats and don't need to be bagged. I don't know whether such a bike requires a 5-10-15 euro surcharge (I've seen conflicting info about that question).
My question is about the 90-120 cm size limit and the bag-requirement:
What happens (de facto, not de jure) if I would step on a TGV/THALYS and my bike is demounted (both wheels taken of), yet it is not bagged?
I want an answer both for the case where the bike frame does meet the mentioned size-limit and where the case where it marginally exceeds that limit (e.g. the frame is 90 x 145 cm).