This is great to see. Hopefully you are right and their are no cuts to the LHR service as a result. The LHR service was cut back quite substantially to the current levels a few years ago after Flybe introduced BHD-LCY flights, and from what I recall Flybe had quite a few rotations a day. The BA Cityflyer might just be mopping up demand from the void left by Flybe.
Anytime I have been on the BHD - LHR flights they appeared to have a large percentage of connecting traffic, so maybe LCY will serve a different market largely business traffic between London and Belfast.
BE were doing 6 rotations per day just before the end. I think some of those in the middle of the day weren’t heavily loaded but were positioning aircraft to and from the peak flights. The early and late flights were rammed, and remember there are curfews at both ends along with a longer flight on the Dash8 and due do circuitous routings into LCY.
That said, BA will need to understand the imprtance of the night stopper. A 1945 dep from LCY to give a 0630 dep from BHD arr essentials for the day tripper for business (if there are any of those left?) BA fell down on this on BHD LHR before and lost a lot of business to BE (who had the advantage with a BHD crew base). EI have also always had this problem on the route with no early arrival into LHR making it of limited use for business traffic.