I assume this was actually on a MF route?

Agree that it's difficult to say without being there, but I think BA possibly did this because the cabin was 6/8. If the cabin were 8/8 I can't imagine how it wouldn't materially affect the service. If you feel the service wasn't up to the standard you've experienced in BA F previously I think you should absolutely complain, making clear you aren't criticising the crew member who did their best in the circumstances (but don't expect it to necessarily lead to anything in return).

1 crew member is definitely pushing it for F, possibly too far. BA is already in the less attentive service tier with 2 crew members for 8 (the likes of JL and GA staff 3 for 8 seat F cabins).