WiFi 6 barely better than WiFi 5 in real world throughput

I got two new Huawei AX3 routers and have them as APs, with ethernet backhaul on my gigabit ethernet main wired router. My ISP delivers 900mbs real world to my laptop consistently when I’m wired to an AX3 or directly to my main router.

I got a Galaxy Note 20 (WiFi 6, 4×4 MU MIMO, 160MHz), so in total have spent a fair bit of cash upgrading. It reports having a WiFi 6 connection (via 5Ghz).

• My old phone on WiFi 5/AC gets ~450mbps up and down, next to each AP
• My new phone barely does better with WiFi 6, all other things remaining equal. It gets close to 500mbs in bursts at best. Upload is always faster and more consistent, and download can be quite patchy.

I have repeated the test with no other devices connected to the SSID.

What is happening here? I know WiFi 6 brings more than just throughput, in the form of concurrency efficiencies. But literally all the write-ups (and of course manufacturer marketing) promises MUCH higher speeds… even on a single channel.

Where can I start to troubleshoot? I’m realistic about real world being much lower than marketing, but I can’t get past the fact I’m not much better than Wifi 5/AC in terms of raw throughput.

Edit:

Just adding that I changed to a S20+ and have the same experience. I guess what I really want to know is whether the AX3’s are the bottleneck, and whether I’d get closer to my wired speeds with another WiFi 6 router.

Edit2: I got a WiFi 6 card for my PC and am getting similar results.