If I recall correctly, that exact example is used in part of the discussion about " Why Literal Application of the Rules Creates Nonsense".
(I guess I need to go back and refresh myself if that is not the case - can you point to where it is, there is so much!)
I think it is only theoretically necessary, due to nonsense determination of seki in some cases. For example, in Diagram 15 of the rules it says that you would need to fill in that dame, but as far as I can see it is quite clear that both groups are alive and have territory.
This nonsense hinges from this regrettably simplistic statement in the rules:
" " Stones which are alive but possess dame are said to be in " seki ."
I recall reading that even the original author regretted this. It is not in the spirit, nor even (as I understand it) reflective of how it is played live (though I am on shaky ground with having no experience there).
But certainly that is not how it is interpreted at OGS.
At OGS, no-one is required(*) to play at A in Diagram 15, and unless there’s something I’m missing, the black group in the above picture is alive (but I still can’t find that example in the commentary to check if I’m missing something).
(*) Note: I’m just one person stating an opinion and observation, not the official rule-maker of OGS. Because I"m a moderator, I do find myself having to make calls on these things, and that’s why I’m interested. So what I’m saying is reflective of how I would currently call it. But this is a discussion… if I’m wrong somehow - entirely possible and likely - then that just gets noted and fed back into future debate/decisions.