Er, not really, did Rab design the zip?. Zips fail because of wear and tear, contaminants, and folk howking at them blindly forcing them up or down.
Er, yes. Rab chose the zip, there aren’t that many parts to a coat, so you’d expect them to check that the zips that they use are of sufficient quality, last x cycles of being open and closed, are tolerant to a reasonable about of misalignment when being opened and closed, etc.
Contaminants and people blindly forcing them up and down would come under abuse, although in the case of contaminants it is unreasonable to expect none whatsoever, unless Rab expect people to do their zips up in a vacuum.
As others have said, they shouldn’t enhance their reputation by offering what appears to be lifetime warranties and easy repairs, and then change their mind as they see fit. I really like my Rab gear, but I will think twice for future purchases.