Other circumstances are less clear cut, for example if riding alone another rider catches up with me and finds my flashing light annoying I'd expect them to continue past me. They cannot expect me to change what I am doing just because they want to wheelsuck. How would they even be sure I am on the same event?
You don't have to be wheelsucking for another rider's flashing light to be a nuisance. They could be some distance up the road and still be annoying, especially if it's a very bright light. And if the speed difference between you isn't enough to close/grow the gap quickly, you could end up stuck with it for a while.
I used to use a flashing rear light, for safety, but the more I read about it, the less convinced I am of the supposed safety argument - it seems to be based on very flimsy evidence. I think there might be more of a case for flashing lights in an urban environment where you have lots of competing light sources, but no case at all on an unlit country road (in fact, flashing lights could be
less safe in that situation because it makes it harder for car drivers to judge the distance between you and them).
Anyway, I no longer use flashing lights.