Depends; your example (乇乂ㄒ尺卂) would be a truly stupendous coincidence if it were the only extant example of something and the Chinese characters just happened to be arranged in that way, but would be much weaker evidence if you had gone mining through thousands of characters and cherry-picked one five-character string that happened to match something. It would be an even bigger coincidence if those five characters, in sequence, were found, by themselves, on a document created in an English-speaking or Latin-alphabet-writing region.

So if all of the handful of fragments have marks that look like actual alphabetic symbols that were actually used in that area (later), that's substantially stronger evidence than you're giving credit for.

Is it worth inquiring whether people who acquired PhDs and have spent lifetimes studying this subject, and (I think) years studying these particular objects, would overlook and be fooled by the most obvious issue?