32c tires technically do fit.

Wheels: 30mm external, 23 internal
Tires: 32c GP5000 S TR, actual measured width 32.5mm

Fork: 2mm clearance all sides.
Chainstays: about <2mm of clearance.
Seatstay: about 2mm.

On perfectly dry and debris-free roads it probably could work. However, I would add some frame protection to prevent tire scruffs. And I wouldn't run any wheel narrower than 23mm internal. The bulbous effect of 32c tires a 19-21mm internal wheel would for sure cause rubbing.

A great compromise is a 28c tires on 23mm internal wheels because it plumps the tire to 30mm. This is what I run on all my road bikes.