Exactly right. Even the theistic evolutionist must acknowledge that once G-d is put on the table as the one who created the first life from which all others evolve, then he has to see that the same G-d could have created it all. Unless of course they believe that G-d was powerful enough to create the first life but not powerful enough to create all life. They could argue that G-d just chose to create through evolution, and I guess that is one possibility, but certainly another possibility is that G-d created it all. Then the evidence becomes subject to interpretation depending on your view. One man's evidence for common descent is another man's evidence for modular design.
If you take G-d off the table and say it all must be explained by natural means, then there is no credible explanation for how life originated.
Importantly as much if not more...if you can convince man that he evolved thru natural selection and such...then there is no creator....thus no G-D.
The whole idea behind Darwinism....eliminate G-d by replacing His acts with "something"..."anything" else. Glorify mans ability to "create" an illusion and one wins half the arguement.