I felt that same sense you did before remembering, "Oh this was a play"

Moonlight was based on a play (albeit one that was never produced) but really only feels like it during the diner scene.

Foley's "Glengarry Glen Ross" very clearly feels like an play (similar to ONIM). I think it depends on various factors/choices like if the play is largely set in a single-location or central interior location, over a condensed period of time, with a small cast and is very dialogue driven that would play a significant role shaping the adaptation. In ONIM's case, the sense of being constrained and "yo, are these fools gonna leave this damn room?" is important to the central themes and the blocking of the actors takes on takes on added importance as it would in a play where you don't have the ability of camera angles/the edit (albeit less-so because King still was making a film and cinematography/edit is really important esp. when the crux of the story is characters talking)


Off the top, I think musicals or plays of sweeping scope/scale would allow for more flexibility. While they did a filmed performance version of "Hamilton," you can very clearly see how a movie version could feel nothing like a stage play beyond the musical elements due to the sweep of its scope.

While they chose to do a filmed performance of Hamilton.

Another set of examples Friedkin's adaptation of Letts' play, "Bug" (largely set in a hotel room with very few characters) vs. his adaptation of Letts' play, "Killer Joe" where you could easily not know the latter originated as a play( due to the multiple locations, larger cast) and just think it was a small little indie film.

Like all things, I think it comes down to the source material in terms of both content and structure and therefore it's not really a protocol beyond "what's the best way to tell this story?"