Your extreme example of evidence in a creator is a valid point, but only to a certain limit. Maybe the grand creator does not want to make things that obvious? Maybe he puts just enough evidence in the universe for people of sincerity for the truth to be lead to the conclusion of design, and not an inch more? The point is we dont know, and the fact that God is not coming down from heaven and telling us he exists is NOT rational evidence that he does not exist and is not the designer of the universe.
As to those Christians who believe in evolution, they have simply developed a personal theology and see science to that end. They are no different from the other religion views, or no religious view.
The real battle is not in science, it is in these ‘world-views’ that cause us to see science in a particular way. I’m not saying we cannot debate what is the truth, only saying that the debate is a little deeper than saying ‘sciences says this’ or ‘science says that’. The debate is more abstract and rational than it is empirical.
Biology textbooks reflect the belief that “The world is purely physical/material in nature” by not even entertaining the possibility that there could be a super natural cause for anything. Any natural activity is assumed to have a physical/material cause. This is philosophy, so it may not be physically written out that way in the biology textbooks, but everything in the textbooks points to this major world assumption.
Same with the issue of free will. Any act by a species is seen in a way that needs to be explained in chemical/biological/mechanical manner. There is no room for this mysterious/other-worldly notion called free will.
Same with the idea that there is no real purpose or meaning to the universe.
As for this statement:
If for example a person does not accept that all of existence is physical in nature, then he is more likely to question the ‘evidence’ of evolution.
It is not necessarily true because of specific theological beliefs only. Lets say a person has absolutely no theological beliefs from any religion, but he does not automatically assume that all of existences is physical/mechanical. That person, because of this world view by itself, now all of a sudden has a higher chance of rejecting evolution than someone who only believes in a physical/mechanical world view.
The real debate is on the level of philosophy, not science. That is because ones science is driven by his philosophical interpretations....whether he realizes it or not.