You guys really don't get that straight air thing at all, do you?
First, it's not that "The Olympics" came up with the straight air requirement. It's actually the other way around, that has been a part of snowboard halfpipe for ever, kind of keeps it from getting too freestyle aerials and forces at least one part of the run to be more about style than technicality.
Second, it doesn't have to be a straight air, it is a "standard maneuver" which is defined as anything with 180 or less degrees of rotation. So air to fakie, alleyoop, switch straight air, etc can all be used as well.
Third, even though having anything be "mandatory" in a run is stupid as hell, 95 % of the boarders still see tricks like that as part of complete pipe riding and still do it even in the events when that rule is not in place. Personally I think it looks awesome to see a massive method in a pipe run, mixed in with all the big super fast spinning tricks, it's a sign of staying true to the skateboarding roots of halfpipe and, if done right, can be the best part of a run.
But anyways, they have the standard maneuver rule snowboarding because that's what they do in snowboard pipe events. There has never been a mandatory trick requirement in any ski halfpipe event (including the FIS pipe comps), so you can guarantee that they are not going to invent a mandatory trick requirement for the Olympics.