Yes, I don't think it's a Slavic subclade. But I think it is possible that it was carried by Slavic people (maybe an other Indo-Eruopean speaking group?) into the Balkans. but I'm still not sure who were the original I2a-din folks.
I think they were native Europeans from somewhere around the northern shores of the Black Sea. So it's a combination of paleolithic continuity and the Slavs.