I can understand your frustration with not knowing when to rest, but it's worth noting that the point of a long rest is not only to trigger a conversation at camp. It's also essential to replenish resources such as spell slots and abilities that require a long rest to become available again, as indicated in their tooltips.
I know how D&D works
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The issue is that because resting takes resource (at this point almost unending resources but still) in a form of food, so systematically the game encourages to rest as little as possible. In general, I aim to use as little of the resources as possible - in case of BG3 I tend to use very little of them, as in most encounters they are not needed to win decisively. As such, when playing BG3 EA I tend to use long rests to trigger cutscenes, rather than replenish resources.
Tying story content to long rests is a troublesome design. It as if Larian tied story progression to how many healing potions player drunk. Sure, they are likely to use some, but if they are playing efficiently they might use one or two or even none.
I suspect the bark is there to remind players to rest, rather than being tied to anything specific.
