I am not sure anyone can hold any one-sided-only view applicable to everyone. Everyone is different and will have a different experience. Some techniques may be more adapted to some individuals, and less to others. I don't think there is any general rule.
As to the time it takes before getting to stream entry, some people have their five hindrances strong, so it will take time at first to weaken them. Some people have them weak already. Goenka told the story of his friend who became sotapanna on the third day of his first course (under Sayagyi U Ba Khin), even before vipassana was taught.
And to quote the Buddha himself on this matter (translation by Bikkhu Bodhi):
So it is clearly shown here that there is difference in people's progress according to inner dispositions