Already exists, it’s called MU-MIMO in the 802.11 world.

Edit: Just to expand on this a bit… typically, the nulls of an antenna’s radiation pattern are sharper (in terms of dB per degree) than the peaks (and this is true for both phased arrays and traditional antennas).

In other words, you can shape the beam to put one receiver in a very deep null while only slightly reducing the RSS at the other receiver. Do that for two beams at once, and each receiver gets (almost) as much power (from the intended beam) as they would if the beam were steered directly at it, while getting very little power from the other beam.

Adding more elements to the TX side enables a greater number of and deeper nulls.