First of all stop getting your panties in a bunch.
There were tons of people aware of BTC on launch and there was not just a few that mined during this period. all the Cypherpunks newslist knew and I knew from the F@H chatrooms and that alone was a huge community so this could be anyone.
That is basically my point. But the flipside to my point is, THIS particular "anyone" is most likely AWARE of what they are doing, and what it looks like. It's not like someone from the mailing list went.. oh shit? You know I am never tried a segwit address.. let's try that? Or he John. I know i owe you 10BTC let me just pay you from one of the first 3500 blocks ever mined.
I totally agree this is not panty wad material. At least not yet. And most likley never.
Though I would NOT be surprised if this is a prelude to SOMEONE getting their lunch handed to them.