That is a rather large leap considering what we know about Bwon.
He’s shifty, but he’s also been shown to be VERY possessive of the souls he keeps; and surprisingly professional about the souls he’s caretaker for. Hell, the entire dogma around Bwonsamdi is that he’s SO possessive of the souls he’s due, that Trolls are not supposed to practice ANY form of necromancy (because its denying him what is his). Hence the reason ONLY the Darkspear and Zandalari have managed to remain in his good graces over the years. He even offers Talaanji an out to her father’s deal with him if she gives him Sylvie’s head.
Bwon may have a boss … but I remain uncertain if it is the same entity as the one Sylvanas is currently feeding.