Server Management Protocol can print strange message on server console

How to Reproduce

1. Start minecraft server with opening server management protocol, then requset this:

{"jsonrpc":"2.0","method":"minecraft:serversettings/allow_flight/set","params":[true],"id":1}

1. See server console message.

Expected Result

RPC Connection #1: Update allow flight from false to true

Observed Result

RPC Connection #1: Update allow flight from [false, true] to {}

Also affects methods serversettings/motd/set, serversettings/accept_transfers/set, etc.