FWIW, for this very reason, there is refresh.metered=hold, as I note in my comment earlier in the thread.
Can I mark all my network connections as metered?
And I'm pretty sure NM lets you set all network connections metered, i.e.
nmcli connection modify $CONNECTION connection.metered yes
See https://unix.stackexchange.com/questions/364927/networkmanag...Canonical should be up front about this type of information.