I truly believe it's the child's make up that determines whether they sleep through early or not.
Eldest was an excellent sleeper, still is. Deep sleeper too. Slept 7-7 from 6 months. Only woke twice a night from tiny. Mainly BF with odd formula bottle. I think it was probably coincidence that solids coincided with sleeping through.
Middle, terrible sleeper and still at 10 doesn't need as much sleep as eldest. Finds it hard to fall asleep and wakes easily. BF. Solids made no difference.
Youngest, mixture of both.
I think consistency of bedtime can help create expectations but is no guarantee.