"....incompetent drivers giving the bike a nudge when parking...."
Bit random, and as likely as being bent by a pram or shopping trolley!!!
And at the moment there is no real evidence to suggest a new disc is needed at all yet, not until he's done a few tests anyway?
Well, not really. Cars are heavier than a pram.
The OP has measured the disc runout and it's out of spec. Which is evidence.
Generally a sticking piston causes the disc to warp i.e. become dish-shaped, because the force is applied evenly around the disc. When that happens the brakes become very spongy, yet there will probably be no runout. Fizzy's disc is bent, which is more likely to have been caused by external force.
As i explained earlier, the best test is to swap discs and try it out on the other side on it's own, but even that's not foolproof, as i found out when mine turned out to be my braided brake line! But he may find that the disc works fine on the left side, only one way to find out though!
Just for the record i browsed through my previous posts with the problem i had and i was
very specific in detail in all the things i had tried and tested (several times), and out of 3 mechanics and this whole forum not one person suggested that the brake lines could be my problem (including myself).
That's why i'm suggesting keeping an open mind at the moment, because i spent a lot of time and money finding out the hard way before fixing it!
And that was only because it was the last thing possible to try
Yet when i first had the juddering on braking, me and the rest of the world said warped disc straight away, and it made perfect sense, because it gave off all the right signs.
Certainly wasn't the case though.