Looking at some upcoming reservations on the app, I see I can add them to my Google Calendar.
Kind of.
They show up on my phone's calendar, but not my desktop. I just added an itin from DL from my desktop, and a meeting from my phone. Everything syncs like they always do, except the Marriott dates.
I really just wish I could add a reservation to to my Calendar with a couple of clicks like I can with Hilton's site (cough, cough).