Traffic capture on VRRP Backup member running on Gaia OS shows that it sends BGP traffic to BGP peers (specifically, BGP "Open" messages).

Output of Clish commands "show vrrp" and "show ipv6 vrrp6" on VRRP Backup member shows:

HostName:0> show vrrp 
VRRP State
    VRRP Router State: Up
    Flags: On,MonitorFirewall
    Interface enabled: 1
    Virtual routers configured: 1
        In Init state 0
        In Backup state 1
        In Master state 0

Output of Clish command "show bgp peers" on VRRP Backup member shows "Active" in the "State" column.