Baby putting himself to sleep but...

My baby will be 4 months in two days. He has very recently (like a day or two) been able to put himself to sleep with no patting/shushing. At least most of the time. But even when he puts himself completely to sleep, he is still not connecting sleep cycles and wakes up and won’t go back to sleep until I pat him. I’m not putting him down too drowsy either, he’s been fully awake and then fussing for a few seconds and going right to sleep.

Is this just the next phase before he can do all of it himself? How long will it be until he will put himself back to sleep if he wakes up? TIA :)