I remember that network traffic feature being dependent on device and the location of the notch.
On my Essential PH-1 the feature briefly showed up in Settings (Pie) after a new installation and then disappeared.
I briefly mentioned it here…
…but I can’t for the life of me find the info I read about that. Not even sure that’s still the case now.
If I remember correctly, even though the monitor could be positioned on the statusbar, on the lockscreen it could not. Devices with middle notch would have the monitor obscured as it was displaying behind the notch. On such middle notch devices the feature was removed.
More searching and I found that it still seems to be the case. Notch = no network traffic monitor.
The Poco F1 and Fairphone 4 have notches. The Xperia Z5 and Fairphone 3 do not so they get the network traffic monitor.