Found a bug.
If you send from one account to another account (Steem->Hive) it sends a memo to the destination account on Steem even though it was never involved.
For example, I sent Steem from one account to @themarkymark on Hive, but @themarkymark got a summary memo even though it wasn't the destination (Hive @themarkymark was).
Got it, thanks :)