We fought this BS years ago when 117 first started. FM-1 used to say you were on duty for 15 minutes after block in to complete post flight duties. This never changed after 117.

as a result they have a choice:

A. Add additional legs before you block in, as your Flight Duty Period ends when the brake is set without notification of additional flights. Since you’re not required to have an internet capable phone they should have somebody meet the plane with the message. ACARS is not official notification per the CBA last I checked.
Now, if it’s not already on your schedule you could argue the FDP ended with brake set and a manager on the jetbridge to make notification is not relevant since the brake was set. I’d probably ASAP that one if it were me.

B. Contact you in person or by phone after block in with notification of 10 hours rest before your new next FDP.

C. Keep your FDP running the full 15 minutes post flight; last I checked they stopped at block in. So, once the FDP ends you’d need 10 hours rest.

9 years later and they’re still playing the same games.