The LAM rules have not changed at all.
There is a rule that says you crash "if a unit converts from fighter to battlemech mode while airborne". There is no such rule for converting from fighter to battlemech mode while not airborne. There are rules for landing a fighter, that's how your fighter becomes not airborne. When your fighter is not airborne, you can ignore the rule about crashing from converting from fighter to battlemech mode while airborne.