Need help making Wireguard Client use specific wan connection

I tried using

option tunlink 'wanb'

on my wireguard peer section and ran some tests.

Firstly, which is good, everything seems to work as usual, no other services seem to be impacted by the change.
But I also found out the VPN connection was still up after I manually removed the ethernet cable from wanb interface, which I suppose means it was somehow using the wan interface.

So, my question is: Do I also need to change the mwan3 policy from current wan_wanb to wan_only, or maybe something completely different?