It is tested and working.After all it is a collection so we can remove its element.
I've tried it and it doesn't work I checked if the route with the name "AddProductToCart-Details" was present in the collecction before deleting it which it wasn't so yeah sure I can delete it but if nopcommerce adds it after I add mine there will always be a fault.
Plugin routs initialize after the nopweb routs there is no chance that after deleting the rout from rout collection at plugin, nopcommerce will add it again.