That is exactly what I did. My background in bio was weak so I went out and got cliff's AP and read the whole thing while repeatedly going over the material I didn't really understand. Also it would be handy to have a laptop near you because sometimes they don't provide as many pictures.
But yeah, after I read Cliff's I went and did Destroyer and found myself to have understood 99% of all the questions in there. I may not have gotten them all right but at least it all made sense to me and I wasn't left asking "Huh, wtf is a ligand?! or a ligase?!"
BUT there are a couple of questions in there not entirely covered by cliff's. What DOC was talking about is that there is a question that asks about what is present in prokaryotes and 'mesosomes' is one of the answer choices. I didn't know what that was and I too have never heard of it before, but in the explanations they clearly explain that a mesosome is ismply an invagination of the cell membrane.
Another question asks about some random kangaroo's diet. And one question asks about the best way to determine where a protein is located within a cell. BUT like I said, those are only a couple of weird questions and the vast majority of the other questions are 'normal' and covered well enough by Cliff's AP. Plus for the weird questions they do a good job of explaining them in the back.
I haven't taken my DAT yet so I can't say if cliff's ap + destroyer is a 1-2 knockout but I sure hope so.😀