Odd implementation for Advent Diplo ship ability

Is it just me, or does the current implementation of the Advent diplomatic ship's ability to increase another teams culture spread badly/miss implemented/bugged? It seems to be spreading MY culture, not theirs, when I use it on their planet. Equally, it seems to spread their culture, not mine, when they use theirs on my planets. This can be particularly annoying when your trying to wage a culture war and your ally keeps disrupting your efforts.

Is this a bug or intentional?