In theory a vertical wheel rotation is better, could lead to more symmetric results. But the main problem is being able to view the blade as it is being sharpened - which is probably better with horizontal rotation.
Sparx and Prosharp are designed for automated sharpening, so that doesn't matter.
As for the amount of metal removed - several good professional figure sharpeners quoted .003" removal per sharpening to me as about right. From what I have been able to tell, that's mostly a matter of the minimum removal amount a high speed grinding tool can do smoothly, and leave a reasonably clean edge - I don't really understand the reasons why that would be true. You can get away with less at hand-grinding speeds, provided you haven't let the blade go too long (if you have, you need to restore part of the hollow, which requires more metal be removed). (But part of the reason you can remove less with hand tools, is that at slower grinding speeds, you are working and reshaping the metal without needing too remove much.)
OTOH, hockey sharpeners want to remove large nicks, which are often deeper than .01 or .02" or even .03", though .03" would be pretty extreme.
If you assume that a figure blade needs to be discarded after about .1" has been removed (because the toe pick is beyond reasonable adjustment to keep the same relationship to the rest of the blade, because the angle of the tooth means that you can't just keep trimming it), that gives a lifetime of about 33 sharpenings of .003 each. If you skate about 40 hours / sharpening (that varies a lot, as you know), that means a blade lasts about 1320 hours of skating per blade. If you skate 10 - 20 hours/week (that varies a lot too), that is 66 - 132 weeks (1.27 - 2.54 years) blade lifetime. You might get about twice or three times that if the skate tech merely straightens the blade most of the time, though that depends a lot on other things, like the roughness of your ice, your skating style, what type of moves you do, and even your weight. Of course careful hand sharpening can extend that a good deal further - I sometimes try for about .001", if it is still reasonably sharp, and I do only straighten when I can - but extremely few figure skaters or skate techs use hand tools to sharpen. You can also extend it a little further if the sharpener is expert enough to compensate a bit for toe pick trimming angle, by a number of techniques, though it mostly isn't considered worth it, perhaps because the pro shop earns extra money by replacing blades.
Some sharpeners don't even know how to trim the toe pick to compensate for relationship to the rest of the blade at all, so .1" is be more than figure skaters can have removed by them and still skate well. For that matter, I've met many parents whose kids outgrow their equipment before it can wear out - remarkably expensive, but it is what it is.
The reason many figure skaters don't complain is that they don't know better. The blade (hopefully) feels sharp, and they get a clean even edge. They blade just doesn't last as long. But they have nothing to compare it too, because everybody else who uses the same skate tech gets the same results. If everyone they know gets, say, 10 sharpenings per blade lifetime, they have no reason to assume that isn't normal. I met one skater who loved split jumps, but doesn't always do them perfectly, and sometimes broke her blades before they run out of metal.
It might seem that removing, say, .01 to .02" would mean that hockey skaters get many times less blade lifetime, especially since many of the good ones sharpen at least once / game. But it isn't quite as bad as it seems, because you can remove more metal from a hockey skate and have it remain useable - there is no toe pick. Besides, a lot of the ones who get sharpened once or more / game are pros, who get free blades, or are on school-sponsored teams that pay for the blades, so it doesn't matter much (to the players). Hockey blades are cheaper too.
It is possible the amount removed varies a lot even for good hockey sharpeners. It might be, for example, that crashing into each other's blades doesn't happen much at the lower hockey levels - so maybe they could get away with .003" too. It's also possible that the hockey sharpeners I have talked to aren't all that good, and that they remove too much. Most of the good figure sharpeners who will talk to me in detail about what they do are close to retirement, and don't worry much about trade secrets. Most of the hockey sharpeners who have talked to me in detail aren't very experienced or expert, and I wouldn't let them touch my blades.