There are definitely calipers that can't take a 28. And the mounting bolt position isn't a precise norm, there are frames that put the brake considerably closer to the rim than others. And not without reason, the effective length of the caliper arms has an obvious influence in brake leverage.
Classic road bike caliper breaks don't >25mm. 33mm would be cantilever CX brakes. Or a weird type of caliper.
Nit-picking, but 27mm is very common as the "actual width" of tyres branded 25mm.