The game is not linear depending on what type of ending you want to get. That is all.
I suppose the insightful Lonecanuck actually meant something more like "sequential" than "linear" in its customary sense?
I thought myself - reading LC's post earlier - "linear" would suggest no parallel/diverging routes exist, routes that may in turn have potential consequences for the rest of the game (see "Sliding Doors"!).
"Linear" normally = one single (even remorseless) straight line.
A broader term ("sequential"?) - might include such parallel/divergent routes - e.g. set off by different player choices - with (even unavoidable) ongoing impacts for the rest of the game. (> "One thing - leads to another!" .... *)
A different path taken probably doesn't affect the cloud of suspicion, or deep-lying anxiety/pangs/tensions the MC lives under throughout most of the game.
Less still, alter whatever his past life included.
But it definitely seems to affect his **love life** - his blue-balled abstinence or balls-relieving couplings - during the story as we see it .... and, here and there, choose his paths on it!
And I suppose most might agree, the guy's love interest(s) is/are not entirely a side issue in this game! :-O
(pp Team Heidi ...)
(*) And as the old standard goes on (approx.): " Too late - to run for cover! / Mo's much - too close for comfort now! ...")