OP is rightfully worried about the reason for these coins to be on the move, especially with how OKEx doesn't usually transfer coins that way. I hope it's just an innocent internal storage transfer but you never know with this exchange.

I would never recommend anyone to use either OKEx or Huobi. Both have been equally as crappy throughout their existence. OKEx even seems to be supportive of BSV, which is another reason to avoid dealing with them.