Isn't that the same issue here that resulted in felony charges? Border agent was given a duress PIN and wiped the phone for the owner. Now owner is charged.
This requires no action whatsoever from the phone's owner, you could even be unconscious/dead and it would still work.
I think this sums it up for me:
- wipe-on-lost-signal = easier to claim as legitimate anti-theft mechanism. Harder to claim you forgot about it (because you'd have the actively live a life where they don't lose signal)
- wipe-on-found-signal = easier to claim as accident. ("I forgot that little faraday keychain was in my bag, and haven't touched it in years since I was on company project X"). Harder to claim it's a general anti-theft mechanism, as it requires a threat model of someone laying all your stuff out together on a table.
EDIT: Maybe it's in a little pouch attached to the phone itself, and they think it's a find-my-object tracker to inspect, but it's actually a beacon that wipes on detection. But yes, this is getting a little ridiculous in terms of plausible deniability :)