bmessage_encoder function in compose verb is combines recipient and message value to match the BMessage format. (bluetooth-map-bmessage.c:254)
Send it with only "" in the message value, msg2dos function (bluetooth-map-bmessage.c:229) treat it as having a string to perform CRLF validation and returns CRLF by appending because there is no suffix.
This will break the format and send message to the recipient from "END:MSG" to "END:BMSG".