Altitude is determined by direction in alternating chunks of 1000ft. So, say, southbound traffic flies at 29000, then 30000 is westbound, 31k north, 32k east, and then 33 is southbound again.
So at cruising altitudes every airspace can accommodate travel in any direction... the controllers along the way probably didn't even realize that anything out of the ordinary was happening except for talking to a Boeing callsign (as opposed to the call sign of one of the major airlines that typically operate flights at this altitude, Boeing operates its own "airline" in the regulatory sense just for test flights).
ATCs along the way don't necessarily need to get the full picture. Each one is responsible for a zone. They have planes about to enter their zone, they route them/land them and then the plane moves out. Not saying they can't easily get the flight plan and figure it out, but they probably wouldn't normally do it.
But no matter how small the zone is, the point where the plane is to make a 90/180/270 degree turn is only in one zone. That means the ATC responsible for that zone would see it. Are normal planes really doing 90 degree turns?
So at cruising altitudes every airspace can accommodate travel in any direction... the controllers along the way probably didn't even realize that anything out of the ordinary was happening except for talking to a Boeing callsign (as opposed to the call sign of one of the major airlines that typically operate flights at this altitude, Boeing operates its own "airline" in the regulatory sense just for test flights).