I just assumed "blockchain" would fall under Bitcoin Discussion since "blockchain" is one of underlying systems within Bitcoin and I thought I've seen many "What is a blockchain?" and other such threads there.
Those threads fall into Bitcoin Discussion since they aren't directed at anything else, just the underlying technology that is used in Bitcoin. In the case of your thread, you are discussing the underlying technology (the blockchain) oriented directly towards altcoins. Consequently, this is why it was moved to the Altcoin Discussion section.
So I guess you are correct and the reason is because it addresses the current Ethereum issue (knee jerk to altcoin).
He is correct.