AX200 
$ iperf3 -c 192.168.0.254
Connecting to host 192.168.0.254, port 5201
[ 5] local 192.168.0.248 port 55570 connected to 192.168.0.254 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 88.9 MBytes 746 Mbits/sec 0 880 KBytes
[ 5] 1.00-2.00 sec 92.5 MBytes 776 Mbits/sec 0 987 KBytes
[ 5] 2.00-3.00 sec 92.5 MBytes 776 Mbits/sec 0 1.22 MBytes
[ 5] 3.00-4.00 sec 92.5 MBytes 776 Mbits/sec 0 935 KBytes
[ 5] 4.00-5.00 sec 91.2 MBytes 765 Mbits/sec 0 48.1 KBytes
[ 5] 5.00-6.00 sec 78.8 MBytes 661 Mbits/sec 0 1021 KBytes
[ 5] 6.00-7.00 sec 86.2 MBytes 724 Mbits/sec 0 1.89 MBytes
[ 5] 7.00-8.00 sec 96.2 MBytes 807 Mbits/sec 0 1.01 MBytes
[ 5] 8.00-9.00 sec 90.0 MBytes 755 Mbits/sec 0 905 KBytes
[ 5] 9.00-10.00 sec 92.5 MBytes 776 Mbits/sec 0 1.32 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 901 MBytes 756 Mbits/sec 0 sender
[ 5] 0.00-10.01 sec 899 MBytes 753 Mbits/sec receiver
iperf Done.
28:00.0 Network controller: Intel Corporation Wi-Fi 6 AX200 (rev 1a)
Where's your iperf3 server? Maybe it's 100mbit itself?