I also heard this comment and the explanation for it. My take was that Fleck has stated that he prefers that his OC also be the QB coach and that he has had the OC/QB coach call the plays. That OC/QB coach has been in the booth rather than on the sideline. If those patterns hold, that suggests that Harbaugh (QB coach who has mostly worked from the booth) would most likely be the one to call the plays rather than Simon (WR coach who has worked mostly from the sideline).
I didn't take it as Burns reporting that he's been told that by anyone, just that it's what history suggests. Fleck could just as easily ask Harbaugh to coach the QBs from the sideline and move Simon up to the booth to call plays or let Simon call the plays from the sideline. We just don't know yet.