I just bought a used T5 and confirmed that, yes, the T5 does send a MIDI Start/Stop when you press the Sequencer Play button. As a consequence, I was able to MIDI start and sync my drum machine perfectly. I can even change kits on my DM and the T5 doesn't miss a beat.
I asked Sequential a year ago to consider adding MIDI Start/Stop to the Prophet 6 several years ago and it never happened. Sequential also confirmed that neither the P6 or the Trigon-6 have this feature at the moment. Too bad...
You may have to turn 'Arp Notes' off in globals if you only want the drum kit. This is what I wanted for my work and it works great.
Bravo for the T5.