... it does normally mean no new major features get implemented.

Which is exactly how every "abandoned" version ends up (e.g. 7.11). What makes "long-term" different from other random "abandoned" versions is that it's not abandoned, instead it does receive occasional fix due to security issues. Which means that latest v6 release isn't that. There are four items in change log:

*) console - updated copyright notice;
*) routerboard - added "reset-button" support for RBwAPR-2nD device;
*) tftp - improved invalid request processing;
*) timezone - updated timezone information from "tzdata2023d" release;

And IMO at least two are definitely not fixing security issues (first and last item), one is highly questionable (support for reset button may fix a bug, but it's not a security issue per-se) and one I don't know (invalid request processing in tftp might be a security issue). And due to changes not really necessary this release requires stability testing before installation on "long-term only" devices ... which could easily be avoided if MT released into long-term chain only minor changes which are "life savers".

But then ... we all agree that MT's way of naming chains doesn't correlate much with what most of users expect ... and the lack of decision making is obvious as well. Like: is development of v6 officially terminated or not? If yes, then only security fixes should be done and (after due testing) pushed directly into long-term chain.

Somewhere in the past someone said 64Kb was more then enough for any PC

It was 640 and kB ... but yeah