I understand the technical points, Martin, thanks for the feedback.
My concern was that “supporting” is more than just being able to “upmerge changes” and “doing the release”, but really have these old releases “available”, tested and awaiting bug reports. If someone now opens an issue and tells you “this happens in my 6.0 installation” you cannot tell the person to “first update to 6.3 LTS and then we talk about it”, you have to “support” it also (even if it might be already fixed in 6.1).
Sometimes bugs are not “code bugs” but conceptual bugs which could be fixed in the next minor version. You do not gain the benefit of dropping the support of the old version with this model.
As I understand this has not been a problem in the past, which is good, but maybe it happened due to the fact that its not so widespread as TYPO3 is. My comment was associated with the known fact that the “people” resources are limited and these should focus in solving issues in “newer” versions rather than in “older versions” - while still maintaining some sort of stability for people needing that (the “agency sickness” you mention).
I did not understand your last point. There is currently no benefit of sticking to “6.0” if “6.3 LTS” has the same end date, so this rises even more the question (to me) of why keep supporting it.
But there is need to do anything, just keep that in mind that there are other options also.