Of course, only a tiny number of wickets come from what I tend to call RUDs (realistically unplayable deliveries - as strictly speaking there's no such thing as an absolutely unplayable delivery as an awful shot could mean you played a delivery which you'd never play with a good shot; and strictly speaking a Jaffa is a ball you can't lay bat on). However, a few of things:
1, there's plenty of wickets that come from good bowling and less-than-100%-perfect batting. For instance, the succession of away-swingers followed by the straight ball. The straight ball wasn't realistically unplayable, and had it not been preceded by loads of outswingers would've been an easy one which most batsmen would always keep out without difficulty. But it's still damn superb bowling. For another instance, there's the 2.5 overs of just back-of-length balls that don't move unduly and keep the batsman tied to the crease and keep his score stationary, then the big outswinger outside off just short of Half-Volley length that persuades the batsman to drive and draws the nick to the wicketkeeper. Again, superb bowling - but if the batsman had left the ball, it'd have been harmless. And a really good batsman might possibly do so.
2, I don't mind at all if a bowler takes 4-50 by taking 1 wicket with a RUD, 1 wicket with something akin to one of the scenarios mentioned above, then 2 with nothing outside-off balls that don't move at all and that batsman for some reason edges to slip or hits to extra-cover. Even though the latter 2 wickets involve no credit for the bowler whatsoever, he's still, in my view, bowled well. However, if a bowler takes 4-50 when all the wickets come from poor shots to deliveries that made zero contribution to those shots, that's not remotely good bowling in my view, and simply being flattered by figures.
3, the McGrath 2001-2004/05 case. McGrath, all career, was absolutely brilliant on seaming pitches, one of if not the best going around. And in the Adelaide Test of 2004/05 against New Zealand, he demonstrated something I'd never seen him do before - he got the ball to move off a non-seaming pitch. And he did it again several times in the next 3 years. However, on non-seaming pitches 2001-2004 (which were all bar 3 or 4 games in the time) McGrath never took any wickets through particularly good deliveries. Of course, some of this time he ended-up with poor figures. But often he'd get 3-40 or 4-60 without, in my view, bowling well at all. Hence, I've always said that in that time he wasn't quite as good as he was oft made-out to be. Until Adelaide 2004/05, I also presumed that it'd always been that way before 2001 too, though conversations with someone (Corey) not long after that Test persuaded me that it actually hadn't been, and that he had indeed bowled as well as he bowled in that game pre-2001 too. So I decided I did actually think he was one of the best seamers in history after all. But my opinion of 2001-2004/05 remained.