Antennas are placed obliquely at an angle of 45, 135 degrees for 2x2 MIMO and 45, 135, -45, -135 degrees for 4x4 MIMO because that is how the antennas on base stations are polarized (so-called cross-polarization).
If you place the antennas at an angle of 0 and 90 degrees, part of the signal is lost because the polarizations are not aligned, which means worse speeds and possible connection interruptions, especially if you are in rural areas where the signal is weak.
For the Poynting XPOL 24 - although it is square on the outside, it also has cross-polarized antennas inside, and that is okay. The disadvantage of this antenna is that it is more widely directed, so it also catches interference that degrades the signal quality.
The Iskra P-60 is a narrowly directed antenna, so it does not catch interference or catches it much less, so the signal is better and cleaner, and this directly affects the speeds.