Sounds like we need an experiment. The best one I can think of is to freeze ice in presence of a tracer gas and then check if that gas is released upon melting. I'm not sure I could pull that off. Got any better ideas?
Also notice the radial pattern that the internal fractures take. This is inconsistent with bubbles and perfectly consistent with internal stress due to expansion pressure.
https://www.dreamstime.com/stock-photo-ice-cubes-image179488...
In that photo I see a few gas bubbles, but it is dominated by radial expansion fractures and cloudy high pressure ice in the center. That ice will crack when put in water. Clear ice does not crack.