There is a discrepancy in the BA IT system with regards to Titles too.

When you book a normal revenue ticket your title is not derived from your BAEC account. Instead the title you select during the booking is used.

However, when you book a redemption ticket, be it MFU or full miles, your title is derived from your BAEC account.
I know this since the title I've setup in the BAEC account is not available when booking revenue tickets, and thus I use Mr in this case.