Does WI-FI speed add up?

Question

WiFi

There is an access point EAP265HD MIMO 3x3, 450Mbps 2.4GHz and 1300Mbps at 5GHz. I establish communication on 2 smartphones, and 2 computers via LAN. On computer1 I run IPERF3 in server mode. On smartphones by customers. I start first in turn, on 1 smartphone 350Mbps, then I run it on 2 smartphones showed 450Mbps. Next, I launch the second Iperf3 server on the second computer and redirect the second smartphone to it (Before that, I tested it in the above mode and on 2 computers, the results are identical) As a result, I launch 2 smartphones to the servers at the same time and observe the result of about 150Mbps and 250Mbps, respectively.
The question is, is this how it should be? Why do speeds drop? Has the 5GHz limit not even reached half? Phones have shown that they can do more, the point should carry 2 streams.

Answer 1

The speed is divided between clients, that is, in your terminology, yes, it is summed up.