Earlier quoted context omitted.
It's only correct for modern automatic transmissions. Plus sometimes start/stop. Probably not for old "3 gear with torque converter" or similiar.
Modern manual cars have start/stop technology too. However, it's more convoluted to use. You have to engage the clutch, put the shifter in neutral, and release the clutch again. Compared to automatic where you just have to hold your foot on the brake pedal. Stop/start reduces fuel consumption on test cycles like NEDC for both automatics and manuals, but I'll bet in the real world the benefit is mostly seen with autom…
That's both a long-winded and incorrect way of putting it. If you are stopped, then you're either already in neutral with the clutch released or the clutch is already engaged. There is no other way.
Really, the rule is just "you have to have the clutch released". For experienced drivers of manual transmissions, this is one smooth action.