BA at Gatwick are largely targetting people who want to go on a beach holiday, particularly over the summer. Peak booking period for this begins immediately after Xmas.
Flybe in its previous incarnation had a significant dependency on corporate travel. Corporate travel is likely to see minimal new bookings before about 05 January. Furthermore, UK domestic routes like BHX-Scotland on a prop are not going to attract hordes of beach-seekers booking 6 months in advance - think shorter periods between booking and travel
The new Flybe have just one chance to get media publicity for the initial set of routes; that needs to be timed to be of maximum use, not at a time when potential (corporate) customers are not paying attention and likely to forget the publicity info by the time they need to make reservations
IMHO, Flybe should stay quiet until early or mid Jan, and then go for a maximal publicity boost