I also worried what to do about the seams. I am sure they must want them taped and mudded before you tile them but I'm no expert and haven't researched it but I'd cover them with screen and mortar them just because.
I was worried about the seams expanding between sheets and maybe cracking the tiles plus its pretty dusty if you use a skill saw to cut it. You can use a razor blade which is fine if you just have to do a bunch of rectangular areas but it's a pain on a big job and another reason was as far as building funds were at the time, we were running on fumes so to save $1000 would be a big deal.
I googled a while and read about mudpans and then asked a few older builders I know, if they'd ever done any and was told that's how they used to do it so I thought a bit more about the fiberglass they put in concrete so you don't have to put down screen and my mortar mixer and the bounty of sand you can find in Florida and I came up with this method which hasn't shown any cracks or problems in the last 18 months or so that the floors have been down.