So you probably mean this discussion? https://forum.mysensors.org/topic/10221/disable-cancel-smartsleep-while-sleep-countdown-is-running
What I get from that is that the node will send a message that it has woken up, which makes sense to me, but isn't in the documentation, which is why I was asking my question in the first place.

The reason why I want to know is, that I want to put a receiver on one of these small battery powered chain of LED-lights. The problem of course is, that having the NRF24 in RX-Mode the whole time alone will drain the 2 AAs in like 2 Weeks or something like that.
So I was planing on only waking the whole thing up with the timer interrupt of my ATmega328P and then signalling my Gateway/Controller, that the node is awake, just to go directly to sleep again if no command is given.
I know, that after I am switching it on on whatever interface I'm using with my controller it may take a while to turn the light on, but that's okay, cause it will just be ambient light anyways.

So I thought in the beginning, smartsleep will be what I need, because the controller will buffer the messages till my node will wake up again. But after reading the documentation I wasn't sure anymore.

After describing my use case, is smartsleep what I need?