Night time dryness is not the same as daytime pottying.
It is a physiological development of the organs/bladder/brain connections/myelin nerve sheath development, etc.
It can take up until 7 years old, for it to occur.
And is normal.
My son is 5 and still wet at night.
My daughter when she was 5, she was still wet at night.
Both were in night time diapers at that time.
They do NOT get "confused" about wearing night diapers and underwear during the day. Because I simply explained to them about their body.
My daughter even at 7 years old, had night time accidents.
No biggie.
I also have, waterproof bed pads, to put under my son at night.
That way the sheets do not get soiled.
Every child is different.
Night time dryness has to do with the body's organ development.