I emailed asking their current policy about breakfast as a Titanium (and whether I could book over email to get free breakfast) and received two replies from the hotel.

The first one said "We are pleased to inform you that as a Marriott Bonvoy member, you have the option to make a direct booking with the hotel via email. For your stay, we can offer both room-only and room-with-breakfast rates."

Meanwhile, the second reply said, "Please be kindly informed that in order to enjoy a complimentary breakfast and earn points, we kindly recommend making a reservation through the Marriott Bonvoy app."

So it seems that no, they are no longer offering free breakfast just by booking over email.