Turning it on would be very hard after a crash. Plus if you eject and you turn it on, the "other" people could trace it too. AFAIK, the purpose of F-35s are to be used in hostile areas, not only training.

Also, ever hear of cracking" ? You think hackers in China could not crack that tracker given enough time ? Stealth usually means "unable to track" in case you are wondering :)