But that isn't coffin corner. The "coffin" is a part of a flight envelope where departure results in near-certain horrible outcomes (ie too fast and wings fall off coupled with too slow and the resulting stall also rips the wings off). A lear or any other business jet is designed specifically to avoid any such things. It should stall, but not in any lethal way. And a lear is small enough that no storm should do things like rip bits off the aircraft. A thunderstorm will toss it around like a tennis ball in a washing machine, but wings/tails should not separate from the aircraft.