There is no "manipulation" as far as I can tell from your post. You are just copying files from one drive to another albeit via internet. The usual integrity checks are applied, and if the file is corrupted it should be detected. The only issue to be aware of is that Dropbox does binary differentials of your files. So if you have a version of a file on the server, and you modify it, the only data transferred is the difference between the original file and the new uploaded version. So if you want to save two versions of the same file you have to name them differently before making them available to dropbox. The updated file should be the same as the latest version on your computer. There is lossless compression applied before transfer, but that should not introduce errors or differences.
I have no idea what PT manual means, but I can guess that it is referring to the fact that wave is a universally supported native audio file format that should work in any version of any software your collaborators might choose to use. Project files will clearly not transfer between different DAW software and sometimes between different versions, and repeated conversions between wave and lossy compression schemes, like MP3, will likely not produce the same result at the end of the chain.