Seems innocent enough, right? But there are some critics who didn’t take Quentin’s note lightly, saying that it “antagonizes professional critics” and dampens the appeal of “processing” his films for interested viewers to read about.
That being said, Critics are saying that the “distinct” spoiler Quentin is talking about would be very obvious for any reviewer to not point out, because it’s such a huge plot point.
Some Once Upon a Time spoilers ahead — you’ve been warned!
So what should you expect when you head into theaters? A lot of that has to do with the film’s structure. The movie been broken up into “three distinct acts,” which are really three separate days — February 8th, February 9th, and August 8th of the year 1969
“The stories of Rick, Cliff, and Tate unfold over three days or, as Tarantino says, in three acts: February 8, February 9, and, finally, August 8 — the night when Charles Manson (Damon Herriman) dispatched four members of his “Family” to the house next to Rick’s on Cielo Drive in Beverly Hills, where they found Tate, hairdresser Jay Sebring (Emile Hirsch), and three others.”
Source : https://www.distractify.com/p/once-upon-a-time-in-hollywood-ending-spoilers