It seems it's someone who knows the Hive ecosystem well.

Also, memo 104624678 used by @nightowl1 to cash out was used a lot on Steem (and probably on Hive too), over 1.5M Steem transferred since 2019-05-26, at the start from @nrg and @jamesc1, even @trevonjb but from many other accounts also, so it might be OTC exchange.