I'm not surprised that parents lack knowledge about baby's development as no two doctors/teachers seem to agree about how babies should develop. And if two do agree then by the next week we'll read that new discoveries have been made.
So trust your instincts and remember all children are different. For example a friend of mine walked unaided at 9 months, both my kids walked unaided at 14 months and my father managed to stand hanging on to furniture at 21 months.
Jane