My road bike has ENVE SES 3.4 Disc wheels on it. ENVE always said those wheels are optimized for 25mm wide tires. I put 25mm Conti 4000SII's on them and they measured 29mm wide. Fast forward to 2019 and the 25mm Conti 5000 TL which is reputed to be narrower than the 4000. Because of this, I contacted ENVE customer service and asked if the wheels were optimized for the OLD 25mm tires or the NEW (narrower) 25mm tires. Their answer was yes.
I mounted the 5000TL's up on the ENVE's and they measure 27.5mm wide. Slightly narrower than the max outside rim width -- just as ENVE designed them.
So . . . at least for ENVE, they are telling you the wheels are designed for the stated number on side of the tire while knowing (and designing for) the actual width of the tire. Perfect.