Is the object to see how much poker you can play in an hour or how much money you can make playing poker? Why in the world would anyone be willing to concede their edge just to play more hands? That's just crazy talk, imo.
It's not about playing more hands, it's about the winrate that comes with them.
If you lose a significant enough edge, say go from $10/hr to $5/hr, then playing two tables isn't going to make a difference. You'll still make $10/hr. But if you can either play 3+ tables with that same $5/hr, or maybe play 2 tables with even a $6/hr winrate, your total winrate will go up significantly.
It's basically a tradeoff of edge for total winrate.
That's why you see players like the_vanetian who have played tens of thousands of SNGs, but only have %8 ROI. He's making a significantly smaller ROI than me, for ex, but is still slaughtering me in winrate. Most of the top multitabling pros can play 12 or even like 20 tables.
You also don't need to be that savvy of a player to be able to do this. It just takes practice - I was completely incapable of 2 tables at first, but after a handful of tries at it with smaller-limit tables, I can now do 4 fine, with only a small edge lost.