MR7400 (AT&T): USB tethering remains active after being disabled in both device and web UI

MR7400 (AT&T): USB tethering remains active after being disabled in both device and web UI

M7 Pro (MR7400, AT&T)
Software: MR7400-1A1NAS_04.17
Firmware: NTGX75_10.04.43.00
GUI: M7_ATT_v07.01.80.00
Hardware: 1.0
Client: MacBook Pro (M4), macOS 26.6.2

USB tethering remains fully functional after being disabled. I have set the touchscreen control at Settings > More > USB Tethering to OFF, and the web UI at Mobile Router Setup > Use USB port for to Charge only. Both settings save and persist across device restarts. Despite that, the hotspot continues presenting a USB network function to the connected Mac.

Verified in ioreg while both settings were in place:

"USB Vendor Name" = "Netgear" "USB Product Name" = "MR7X00" "USB Serial Number" = "c5ff0a77"

The Mac receives 192.168.1.4 by DHCP from the hotspot, which the user manual identifies as the address assigned to a USB tethered client. Traffic bound explicitly to that interface reaches the internet and returns:

ping -b en19 -c 3 8.8.8.8 3 packets transmitted, 3 packets received, 0.0% packet loss

I restarted the Mac with both settings in place and the interface came back up unchanged, so this is not stale state on the client side.

Impact: I use the 2.5G Ethernet port as my data path to the same Mac. Because the tethering interface comes up anyway, the Mac ends up with two interfaces on 192.168.1.0/24, both gatewayed at 192.168.1.1 with the same DNS and IPv6 prefix. I have had to disable the network service on the Mac to work around it, and that does not survive a hotspot restart.

Separately, tethering often fails to come up at all when I connect the cable to an already-running hotspot, and does not appear until I unplug and reconnect. The manual's tethering procedure has you power the hotspot off first and connect the cable before booting, which suggests the USB network function is not presented until some point during startup.

Possibly related: https://community.netgear.com/discussions/aircard/mr7400-m7-pro-att/2473181. Same AT&T build, different symptom, but also a settings-layer control not behaving as shown.

Screenshots of both settings attached.