There is, in my opinion, no call for speculation and supposition, Boyer's or anyone else's, other than to speculate about, which is to say question why Wyatt so late in the day fabricated his "I killed Johnny Ringo" story. Moreover, Boyer isn't speculating so much as he is rationalizing because, pardon my French, he clearly has a hard-on for Wyatt Earp, his hero (as well as being of dubious psychological competence) and feels compelled to twist himself into a pretzel to avoid having to gainsay that Wyatt dissembled.
Again in my opinion, it is far more plausible to believe that Wyatt invented that story than it is to believe some cockamamie Boyer-concocted theory that he "compressed the time difference," a theory that rests upon the false premise that Wyatt somehow returned to AZ undetected "months after the Vendetta Ride." The issue is why Wyatt chose to invent, not whether he invented. (We know why Boyer did.)
One other point. Why is Ringo's death the outlier here (save for, maybe, Brocius)? Why the mystery? As I recall, Wyatt was not shy about more or less contemporaneously copping to the deaths of the other Vendetta Ride victims, but he didn't "own up" to or boast about Ringo's until 40 years after the fact. How come? Why this clandestine quality to that particular killing? You would need to swallow wholecloth both Wyatt's "sneaking back to AZ" story as well as Boyer's "distortion of time" conjecture to plausibly answer that question and, obviously, some of us, most of us perhaps find ourselves are unable to do that.
Finally, where are the statements from the other Vendetta Ride members or from the "posse" Wyatt references or even from any reminiscing children or grandchildren that would so much as pretend to corroborate Wyatt's claim? Did anyone at all have word one to say not only over a 40-year stretch, but even after Wyatt's death? Or perhaps those that otherwise could have made such statements, those who knew "the truth," chose silence throughout their lifetimes out of their transcendent, unshaking fealty to Wyatt B.S. Earp.
No, it isn't rocket science to understand even the little we know about the facts of John Peters Ringo's life to understand in turn the reason(s) and circumstances behind his death. With hindsight, which I grant you is not necessarily 20/20, it is difficult not to conclude that Ringo was a dead man walking. His suicide, given the larger context of his life, makes perfect sense. Quite simply, it fits.