I think the call still could (and arguably should) have been overruled by a good knowledgeable head referee, and part of the issue here was that Marcel is not a good knowledgeable head ref (to put it kindly).
In his protest Pongers presumably told Marcel "the ref declared the balls to be frozen, and I shot through the balls with a normal stroke as allowed when the balls are frozen, so it was not a foul". Presumably Marcel then asked the ref why he felt it was a foul when hitting into a frozen ball is legal (or he certainly should have if he didn't), and if the ref said something along the lines of that it was based purely off of the "cue ball and object ball moving forward together at the same speed" Marcel should know right there that is not the measure for whether that shot is a foul or not (since it would have been the expected action) and overruled the call.
If the ref instead said something along the lines of "well it just looked like a push stroke to me" Marcel should have then asked some follow up questions such as "what speed did he hit the ball at", "what made you think it looked like a push", and "did he first put the tip on the ball and then push forward" along with a couple others as needed. When the ref presumably answered with something like "he hit the shot fairly hard, and no, he didn't put the tip on the ball first and then push, he just hit it like a regular shot, it just seemed to me that the tip was in contact with the cue ball a little longer than it would normally be" Marcel should have known that the ref just didn't know what he was doing on the call and clearly made a bad call. With good questioning from a qualified head ref I think there was enough there to overrule the call, although I also understand the hesitation to do so without the ability to look at a replay in this particular case.
One thing is certain. Matchroom refs in general, and Marcel in particular, need a lot more knowledge and training before they are qualified to be refereeing professional level events.