Per Batcher's unique ability, LH-201, "Batcher's damage can't be evaded, and she ignores Stealth and Taunt during her turn." The recording I captured is too large to be sent as an attachment, so ...
Ideas
At this point I don't think it can be attributed to just the taunting unit being a summon. I ran the team against the Geonosian datacron node in sector 4 of conquest, did not inflict marked on any units, and Batcher is able to bypass taunt/stealth in that battle. So far I have only noticed this interaction in TB with the summoned probe droids (Kashyyyk/Mandalore).