I noticed on my 3 antenna MIMO, I get better SNR by orienting the antennas in what I would call the L-finger. The center antenna is vertical, giving the finger. The other two antennas are 90 degrees offset from each other. Maybe orthogonal-vulgar is a better description.
Most of the photos of these 3 antennas MIMO routers have the side antennas angled.
The wifi is going to devices with no discernible antenna orientations. Squeeze devices and phone.