I can’t tell if you’re being serious or sarcastic.
Not sure if you’re seriously claiming that the “blurb” for any book or movie should never mention anything outside of the first fifteen minutes.
Eg, would you promote Harry Potter as nothing more than a story about “a bullied boy struggling with his adoptive family who make him sleep in a cupboard” because the revelation of magic is a major spoiler?
Primer sets up the big reveal as a mystery. It intentionally obfuscates what's going on while dropping hints.
Knowing too much basically makes this part of the story structure a waste of time, and I don't see why the writers and directors would have sculpted such misdirection unless it was to surprise the viewer.
I went in uninitiated and it didn't fully click until the binoculars came out. It made the rest of the movie an absolutely insane ride.
It's a shame people have normalized talking about its premise in the first sentence.