If ROS device needs to communicate with certain VLAN (msanagement, routing), then it’s the only way.
Since you’re mentioning linux: these two are identical:
ROS:
/interface/vlan
add name=e1v100 interface=ether1 vlan-id=100
/ip/address
add interface=e1v100 address=10.0.100.1/24
Linux:
ip address add 10.0.100.2/24 dev eth1.100
It’s just that in linux case, the vlan interface is created implicitly.
However, the magic above doesn’t have much with bridge. Bridge is specific because it has multiple personalities (depending on how one counts it may have up to 4 personalities) without clear distinction in ROS config, so it’s hard to wrap one’s head around it. Reading through this article should help.