Coolant hose replacement.

Here’s a couple more states as examples that will not haul your butt away:

Again, these are just a couple examples. A quick search will lead you to more.
It seems that some municipalities might allow the dumping of used coolant into the wastewater system, but just as you found some links that suggest it's allowable, there are many municipalities and states that don't allow it. I'll concede that I may have been too critical of your original statement.
If you weren't doing the other work, he wouldn't have told you to replace it, but since it's going to be "messed with", it's a smart idea to replace it while you or he are there.

Other than some real OCD types, I don't think anyone replaces hoses as maintenance parts anymore.
I totally agree. When I did my wife's water pump, I undid the lower rad hose to let it drain. When I put it back exactly as it came off, it leaked. Defied common sense. Techically? You're not supposed to even reuse those hose clamps that are under tension. They're usually open the entire time the job is being done (water pump). People don't want to listen, I get it, but there is some truth to if it ain't broke, don't fix it. Maybe an auto trans who never had its fluid replaced and now it's 300k miles, is an example