mt7603 continues to interrupt MT7621 cpu after radio0 is disabled

Test Device:

OpenWrt GCC 5.5.0 r5484-69d22a6 (buildbot)
MediaTek MT7621 Netgear WNDR3700v5

Video:

Steps to reproduce:

1. Ensure mt7603/radio0 and mt76x2/radio1 are enabled in Luci
2. Open a new SSH connection and continually check /proc/interrupts using watch command

opkg update && opkg install procps-ng-watch
watch -c -n 0.1 'cat /proc/interrupts | grep "mt76"'

3. Disable mt7603/radio0 in Luci
4. Then disable mt76x2/radio1 in Luci
5. Note interrupt behaviour
6. Reenable mt7603/radio0 and mt76x2/radio1 in Luci
7. Open another SSH connection and run the commands whilst monitoring interrupts

wifi down radio0
wifi up radio0
wifi down radio1
wifi up radio1

Observations

• The mt7603 processor interrupts increment when radio0 is disabled in Luci
• The mt7603 processor interrupts do not increment using Wifi down command
• The mt76x2 processor interrupts do not increment in /proc/interrupts when it's radio1 is disabled using Luci or via wifi down command

Questions:

• Is it expected behaviour for the mt7603 driver to interrupt even when its radio is disabled in Luci?

Start by reproducing the Luci and wifi down/up sequences on the listed MT7621 device while watching /proc/interrupts for mt76 entries. Compare mt7603 and mt76x2 behavior after each radio is disabled; done means determining whether the mt7603 interrupts are expected and documenting or addressing the confirmed behavior.