> Ryuma was a "Shimotsuki" and Oda already mentioned before Zoro was based on him
> "Shimotsuki" is the old Japanese name for November, the month Zoro was born in(11th November)
So looking at this, it was already implied before that Zoro might be from the Shimotsuki clan, and while it's not exactly confirmed still, it became even likier now with this SBS release