Serpentine belt on 2008 Toyota Corolla

I recently scheduled a repair with a new mechanic. My serpentine belt (replaced about a year and a half ago by the dealership) was pretty noisy when idling. The mechanic said the belt looked okay BUT if I wanted to get my coolant flushed and changed, I should also replace the belt anyway since there was a possibility the coolant would saturate the belt and cause trouble. Beyond checking my oil and changing my air filter, I don’t know a thing about how anything works under the hood of my car, so I went ahead and had the work done.
Is it typical that these 2 repairs must be done together?

Replace as needed, it does not appear to be needed. If coolant leaked onto the belt it might be a possibility, but I would need to know why coolant is leaking

Sounds to me like this mechanic thinks he might spill coolant on the belt while changing the coolant.
So he’s admittedly sloppy.
If the belt is rinsed off with water it won’t be damaged.
The noise (did it go away?) may not be the belt itself. It could be a pulley or tensioner.
If the coolant is changed on time there’s no need to flush, just drain and refill.

If the mechanic thinks he’s going to slop coolant all over the belt, he could remove it first to avoid that. Also, there is such a thing as rinsing it off. He’s really just trying to sell you a belt.

If the belt squeals, it could be the tensioner. If it chirps, it could be a bearing in an idler pulley.