I don't think the 'usage' point is valid to be honest, but I doubt we're going to end up agreeing on this anyway The core use of a 3 series touring versus a 3 series saloon is as different as the use of a 3 series saloon versus a 3 (4) series coupe. Speaking personally, the difference between a saloon and coupe is looks alone - there is very little extra practicality afforded by a saloon for me - so the way the car would be used is identical. I use my Golf GTi for the exact same things as my E30, or my M3 - no difference.

As you said yourself, the models already exist - but BMW have very clearly tried to push the 4 series as being an all new offering, which to me, is patronising to their client base, its a 2 door 3 series really. I've no great issue with the rebranding per se, but I really think its a stretch to say it was needed before of customer confusion.

Although Audi even seem to have lost track of their version of this even nr = saloon, odd nr = coupe branding lark with the A5 getting a 4 door and 2 door version.