Some players are slow starters. Players like Shane and Earl can catch a gear and run over anybody. This is their edge - they learn to channel the momentum to win. Alternate break and sloppy pockets take away a lot of Shane's otherwise massive advantage. This format, as you say, does not suit him in the least.
I'm not sure alternate break is the problem, The problem is that Shane's break is best when the pockets are tight, not loose. Even with alternate break, I believe he'd be awesome in singles on that equipment.
My own experience offers some guidance here. I play pool twice a week (at least when I'm not traveling) and one day it's on a bucket table and the other day it's on a tight table. I make a ball on the break way more often on the bucket table than on the tight one, just as one would expect. Contrastingly, on tight equipment, Shane's ability to make a ball on the break is practically undiminished.
If, hypothetically, I had to play Shane, I'd want to play him on the bucket table, where my break is far more effective than on the tight table. Shane will break well wherever we play.
The easier equipment levels the playing field with respect to the break. It's a reality for me every week! I believe the equipment is more of an issue than the use of alternate break for Shane at the Mosconi.