Break it down this way. The pluperfect, or past perfect, denotes
"a tense of verbs used in relating past events where the action had
already occurred at the time of the action of a main verb that is
itself in a past tense. In English this is a compound tense formed
with had plus the past participle." Collins English Dictionary
Therefore the concept described in the question above, which denotes a situation relating an event which will occur earlier in the future than another future event is, by definition, not pluperfect.
On the other hand the concept is exactly what the future perfect tense exists to describe. Per Collins, the future perfect denotes
"a tense of verbs describing an action that will have been performed
by a certain time. In English this is formed with will have or shall
have plus the past participle."
Random House Dictionary adds the additional details that future perfect is
"perfect with respect to a temporal point of reference in time to
come; completed with respect to a time in the future, especially when
incomplete with respect to the present."
Therefore, "John will have run the race by the time we arrive." is both simple and correct. Attempting to mangle this construction into something approaching a hybrid of past perfect and future perfect like in the example in the question doesn't add any meaning to what is already available in the future perfect, so it creates an unnecessarily awkward construction using non-standard English that has no positive value but plenty of negative value as it can be confusing and can make the speaker sound like some backwoods inbred villain straight out of B-grade scary movie.
So to your basic question, is it real? Obviously some people can and do say it, so it's as real as slithy toves and cooties. But it adds no value. I mean you can go back to monochrome green screen Apple II computers with no hard drives and only a floppy (truly floppy) disk drive and play Zork all day while the rest of us are moving forward with our lives just as you can use this horribly mangled form if you choose. But I'm not and I wouldn't recommend it to anyone else either.