The ever-puzzling rules of Hail & Ride buses

Can anyone explain the Hail & Ride etiquette to me? I feel like I’m constantly breaking some kind of unwritten rule that everyone knows about except me, committing the public transport equivalent of drinking the water in your finger bowl…

The TFL website said that Hail & Ride (as the name implies!) can be flagged down or requested to stop at any safe point along the route. Yet most drivers seem to operate as if there are definite stops (eg. by the gate to the baseball field on Endymion Road, the postbox opposite Hornsey Library etc.) even though these are completely unmarked. I’ve been told off for trying to hail the bus at other points along the route and sometimes it hasn’t stopped at all. If you ring the bell whilst on board it usually carries on to whichever of these invisible-to-the-naked-eye stops is next. 

Except the other day I pressed the button, expecting this to happen and the driver stopped immediately and said “are you getting off then?”  It’s so confusing! Any insight appreciated…