What is the 6a[...] hash in OP_RETURN transactions?
6A is the hex representation of OP_RETURN:  https://en.bitcoin.it/wiki/Script

That is not a hash at all, but rather the raw encumbrance script.  You are looking at the code that actually contains the OP_RETURN.  You can decode these scripts here:  https://chainquery.com/bitcoin-api/decodescript