I don't follow the idea that a baby gets fed in the night therefore somehow makes themself wake up on purpose in order to get fed.
It doesn't make any logical sense to me.
- If you're unconscious aka asleep, you can't just choose when to wake up, if we could, alarm clocks wouldn't be a thing that virtually everybody needs.
- Babies can't tell the time anyway, and also it's the middle of the night, with no time cues.
- Why would you rouse yourself out of a nice comfortable warm slumber in order to cry/scream (doesn't feel nice, hurts your throat, etc), be removed from nice warm bedding into the cold JUST for milk, which you can presumably get any time you're already awake, if your mum is feeding on demand which most people do.
It's like the argument that if your favourite restaurant opened a 24 hour free buffet on the street corner, you'd go there at 3am all the time. No, I wouldn't, because I would be fucking asleep! I mean OK, if I woke up randomly at 3am, and I was hungry, then why not. But I sure as hell wouldn't be setting an alarm clock specifically to get up at 3am and go to the restaurant because that makes no sense.
I do not get it. And I don't see why not feeding them would therefore get them to decide this is pointless and not bother waking up. Which is probably the biggest reason why I've never attempted sleep training because it seems to me to be based on a totally ludicrous premise - the idea that babies while asleep suddenly decide to wake up in order to have milk.
I can see that:
Baby enters a light sleep phase/wakes slightly (as we all do several times throughout the night)
Feels a little uncomfortable with slight hunger sensations/isn't sure where mum is because they fell asleep in mum's arms and now they are alone in bed.
Cries
Mum gets up, feeds, baby is soothed back to sleep.
But I don't think this is anything conscious. It's just a consequence of the fact they are not used to either falling asleep alone or the feeling of being slightly peckish.
So I can see in this case - if you can work out which one of the two it is (and if you're lucky it's not both) - if you can somehow achieve the voodoo of putting them down "drowsy but awake" and get them used to falling asleep in their own bed, or if you commit to soothing them back to sleep in ways other than involving feeding, you might get to a point quicker where they do that slight waking up thing and instead of reacting to that feeling of not-quite-full tummy or "where's mummy gone?" they just consider these things perfectly normal characteristics of night time and roll over and go back to sleep. I could see that working, but I think acclimatising a baby/toddler to either of these things is likely to be a lot of work and personally I just found it easier to co-sleep, which they do grow out of eventually.