Because, and I thought this was obvious, all my comments about the hypothetical greyhound situation involve the scenario where an otherwise under control greyhound slips its lead and kills a cat. This was the scenario outlined originally, which I responded to. It was not about a greyhound that is capable of pulling its owner over, as was the case in the OP's scenario with the bullies. In that instance, yes, the greyhound would also still be dangerous.
Obviously the mitigations for a greyhound that slips its lead are not appropriate for an XL bully that can pull its owner over. A second lead / harness would likely be completely useless for the bully, which remained on a single lead but out of control, but useful for the greyhound, which was only out of control because it slipped the lead. A muzzle alone is not sufficient in this instance either - a large dog can cause injury without biting. That is precisely why I said that there are no sufficient mitigations for the bully situation (unless you include electric collars or similar - I don't).
As I didn't make any comment about greyhounds that could pull their owner over, this is technically irrelevant, but since you bring it up, I know from experience I can hold a greyhound. I can't speak for you, or for anyone else, but it's something of which I have a lot of personal experience. Granted, not if it was on a long line and allowed to get up speed, but obviously you'd be idiotic to allow a dog to do that, in these circumstances, rather than walk it on short leash, sensibly. I don't know if I could hold a dog like those in the OP's situation, but since their owner could not control them, those dogs remain dangerous while being handled by that person, which was my original point.
I'm not going to continue to discuss this with you because you're now changing the hypothetical situation to misconstrue my comments and support your own rhetoric. You'll probably try to do the same to this post, but I presume you're just being obtuse.