I still think that regardless of Spawn Condition, there's still the RNG aspect: So even if players got the Spawn Condition (Trigger) correct, it wouldn't just be set at 100%.
Look at Brontes - I know some JP players who went through over 1,200 Eggs (and other foods) during the supposed open window (we had full LS's doing this) and nothing. And then seemingly randomly, a day later, it spawns (w/ other people eating food).
Looking at other systems in the game, it's the same w/ SE and their "RNG / Rolls": I've had 95% Chance to Gather some items, and I missed 3 Times in a Row (this has happened a few times). (>_>)
And I've also had 5% Chance to HQ and HQ'd something 4 (FOUR) Times in a Row. LOL. Sigh.
Just saying that there's a real possibility RNG / Roll Chance to Spawn also throws a wrench into everyone's investigation into Spawn Conditions. You might've gotten the right Spawn Condition, but RNG Roll wasn't in your favor. Then... [X Duration / Window Closed to "Roll" Again to Spawn] and then it checks again.