What am I doing wrong? Does PUPD actually work?

My 6.5m old wakes 2 hours after going to sleep, regular as clockwork. He goes to sleep very well: I give him a quick cuddle safety his bedtime routine and then he goes in his cot and goes to sleep by himself within about 5 min. It's great!

So, he can put himself to sleep, but the rest of the night is awful. First wake up is always 2 hours after he's gone down. I don't feed him on this wake up because it's usually only 2.5 his since his dinner, so I settle him back down. I have been trying the PUPD method for 1 week now but have not seen any results. He will not go back into his crib unless he has fallen asleep on me and then he'll only sleep 20 min before we have to do the whole thing again.

It's so frustrating because I KNOW he can put himself to sleep.

Eventually we do this PUPD/20min sleep cycle long enough that it's time for him to feed and then he'll sleep for 2 hours and we do the whole damned thing again.

Does PUPD actually work? It seems like it's just teaching him to cry louder so that I'll pick him up. He never settles with the voice or pats before the pick up part, so I don't see how this method could possibly work.

I feel like I'm failing at this training stuff. I have paid a sleep consultant and she has given me this plan but she cannot answer my question about why the PUPD method would do anything other train your child to cry louder. They have no motivation to be patted or voice-soothed to sleep when they know that if they just keep crying you'll pick them up. Can someone shed any light on why she thinks this will work?

I'm desperate for more than 2hrs of sleep...