If you want to optimise for targeting a specific virus, then yes, narrowly targeting the most stable functional element of that virus is preferable to targeting other elements of that virus. If you want to optimise for having a broad response to related viruses, then a less narrowly targeted response is preferable.
I was explaining why there's potentially a difference between natural immunity and vaccine-mediated immunity, and why one of these may well be preferable if the goal is to generate maximum immunity to a widespread virus. But that's not the actual goal, and as a result policy decisions may differ. Is the risk associated with vaccinating people who have some degree of natural immunity justified by any improvement in immunity they gain as a result? I don't know! I have opinions on the matter, but I'm not qualified to make that determination.
