I've read conflicting information about this. As you mentioned, some sources say you can only bill 88333. Others say you can bill 88333 and 88305 if two separate specimens are taken and only one was applicable to the touch prep 88333. And lastly, I've read that you can bill 88333 and 88305 in a scenario like yours IF there's documentation as to why 88305 is also being billed. Specifically, the documentation must clearly show that the information/results from 88305 directly contributed to, and influenced, the diagnosis made.
Personally, I think all three sources could be correct depending on the circumstances and situation. If there's no documentation to support the necessity of billing the 88305, as in it did not contribute to the diagnosis, then you could only bill 88333. And logically, if 88305 could not be billed due to being non-contributory to the diagnosis, then the opposite should apply also; if it DID contribute, you should be able to bill 88305 additionally. If two specimens are taken and used for separate "purposes" (for lack of a better word), then I could see 88333 and 88305 both billed as well. But that's my opinion.
I know that's not really a solid answer, but maybe it can help.