Dell has swapped the 11th gen Intel CPUs for 12th gen options and the Wi-Fi 6 Killer 1650s WLAN for the Wi-Fi 6E-compatible intel AX211. Though the CPU upgrade is notable, the WLAN update is largely pointless as Wi-Fi 6E is effectively disabled on the model.
https://www.notebookcheck.net/Dell-XPS-15-9520-is-15-to-35-percent-faster-than-XPS-15-9510-lacks-Wi-Fi-6E-support-despite-coming-with-an-Intel-AX211.622656.0.html
No 6E? Weird. Any idea whether this is a driver, firmware or hardware limitation?
If it was just the question of updating drivers then they would have fessed up to it and would have said that it will support 6E in the future. My guess is they did not upgrade the antenna and the one they have performed subpar. They could have upgraded the WiFi card itself since the old model was not being manufactured anymore.