It depends on which hold your bags go into.

Some get more heat (the one they put the pets into for example) than others do.

For something in a suitcase to get to the freezing point of wine (generally about 25 degrees but will vary significantly based on the alcohol content) the hold has to be below freezing long enough to chill your bag and whatever the wine is packed in to that temperature and the liquid in the bottle, and hold it for a while. If for example you put a bottle of wine out on your deck in the winter when it's fifteen degrees out, it won't instantly freeze, but will take a while.

I've had things like olive oil congeal (which can happen starting at 40 degrees) on flights, but have never had a bottle of wine freeze.