As with all things watches, specifications on paper doesn’t always directly translate to how it wears on wrist.
My 3 thickest automatic watches are the Omega Speedmaster triple date at 16.2mm, the Tudor P01 at 14.5mm and the Seiko Presage at 12.4mm.
From the side profiles, you can see that the case of the Speedmaster Triple Date is narrow with a significant portion of the height protruding from the case back and the cantilever style bezel. The mass of the watch is below the bezel and the protrusion from the backcase sits in the hollow on the top of the wrist, making the Speedmaster sit low and feels much like a watch that’s about 12+mm thick.
The Tudor, with it’s classic slab sided case has most of its mass on the case, sits high and has the most presence on wrist.
The Seiko also has some mass in the back case that helps make it sit in the hollow of your wrist and feel not too thick.
Moral of the story - don’t judge a watch purely based on specifications. Best to try them on in person.
Profiles off wrist:
Profiles on wrist: