AFAIK default setting is that every port member of bridge is untagged member of VLAN ID 1. Which is true for bridge interface as well and thus completely obfuscating the fact that VLAN ID 1 actually exists in default ROS installation.
OTOH, if some VLAN is passing port untagged (hybrid port), then the information about VLAN ID gets lost … hence if your AP requires “untagged VLAN 1”, it doesn’t matter how untagged is called in ROS, it just has to be untagged over interface connecting to AP. Can as well be simply untagged as per default 