I don't think there is anything wrong with the name Bant Banner mirroring Abzan Banner.

The current name (Bant Borderstone) invites comparison to Wildfield Borderpost which these are certainly not.

Thematically borderstones were cool since their colors fell "in-between" two shards and the new borders were an essential part of the setting. Bant itself is not a "in-between", it's the thing that borders to other things, so the name seems ill-fitting.

Since you seem to return to a united Alara the people of the plane are now aware of the other (former) shards and it seems reasonable to assume Esperites and Nayans etc. will have developped an identity by now based on their common history and understanding of the world.

As such I think the shards who didn't have a need to give themselves a shard-wide banner before (since there was no one else for them to distinguish themselves from) would probably create a Bant Banner etc. in the aftermath of the Conflux.

tl; dr: You should call these banners if you mechanically make them arc-aligned mirrors to the existing wedge-aligned mirrors of the clans.