VLAN Parent Interface Question

[Laxarus]

Hi,

in pfsense + bridged modem setup
Internet is via pppoe on vlan 10

so pfsense port igc0 connected to the modem port
vlan 10 is set up
and ppp interface is assigned, enabled and set up on pfsense on pppoe igc0.10
so WAN is on pppoe igc0.10

It appears If I do not assign and enable the parent interface igc0, pfsense refuses to connect even though the pppoe igc0.10 is enabled. Is that a normal thing?