Im for the latter. If you let it go, you give them permishion to leave something elles out nest time. I mean its in Black & White. I can only think of one thing, the roller door motor is a smaller unit the panle lift is a bit more complex and has the running track, may be thats the difference. However, it only a few hundred bucks. So they should just give it to you.
Its unfair that owners feel they have to tip toe around things like this with the fear of the builder being able to rip them on something elles down the track to make up for it.
KW.............