I'm not disputing there are distinctions. But the key concept is that even in the absence of any source of healing, all damage is still gone the next day.
When you have 100% healing every night, it doesn't matter if the numbers are bigger or "so much less". The result is exactly the same.
To be fair, it is pretty different, because many 4E PCs could, over the course of a day, with, say any Leader (let alone a healing-focused leader), and using short rests, potentially heal 250-400% of their HP (or more!) in a day, even ignoring the "heal to full" at Long Rest.
The big difference was, once they were out, they were oooooooouuuuuttttttt. Used all your surges? Pretty much done healing until the Long Rest.
So I'm not sure that is "the key concept" when responding to that post, but rather "the concept most disliked by you".
Compared to 4E, it absolutely does matter. You are wrong to think that 4E's key healing concept was "heal to 100% on Long Rest". In most cases, unless a party was
truly embattled, they went into a Long Rest on good HP, usually with most of the party having a number of Healing Surges left (as a 4E DM, I'd argue that they actually had too many Healing Surges, but that's another, 4E-specific, thread). So 4E had only had you regain, say, 50% HP, or even 1 HP for a night of rest, but had had you regain all your Healing Surges (as it did), it'd still have been largely irrelevant, as with a Leader, it's typically only 3 HS to get back to full health from zero (it cannot be more than four, even without a Leader entirely). With a healing-oriented Leader, it could be about 2 (certainly to get very near full health).
So anyway, I understand that you dislike "Heal to full on Long Rest", but it's not the key issue for people who liked more 4E-style healing approaches, I would suggest. It's good, if you like that sort of thing, because it reduces book-keeping and so on. But it's not the main deal.