This is true, except:
1) You're most likely going to crash in a race, not a training ride. In 12,000mi I've never even seen a dude crash, except in races
and
2) proper valve extenders work exactly like a regular valve, threads and all. No more of a hassle than normal.
If you rid enough your odds of crashing outside a race are real. Some racers have ONLY crashed in training rides and not on race day.
Even if u are lucky enough to have a reliable valve extender it is an additional point if failure. And I have spent significant time hassling with several valve extenders, none of which have been bulletproof failsafe. All have glitches and those are amplified on a flat on ride . I use Teflon tape to ensure reliable nonair leaks.