In our (now totaled) Santa Fe (RIP...moment of silence....and done.)
Did a complete flush and fill of coolant system at 100K. At 103K, starter died. When changing it out, you have to remove one of the coolant hoses that runs right in front of the bolts for the starter. (The hose turned to dust as I was taking it off, but that's for another thread.)
Had to drain quite a bit of fluid to avoid a big mess. I used a couple of VERY clean buckets to catch the fluid. It all came out looking extremely clean. When job was done, it went right back in.
Car was totaled at 168K, no issues with reusing the coolant.
Maybe they are forced to remove & drain the products you mention to not pollute. And figure while they have it out minds well sell and make some $$. Disposal might cost them so even selling for $2 seems like a good way to handle it.