Not true at all. The only accurate way is to count the rings. There are a lot of factors involved in how fast a tree grows. Species certainly is one, but site, available water, completion from other trees are even more important. You can have two trees of the same species and age side by side; but if one of them gets adequate sunshine and the other is in the shade of another tree there can be a tremendous difference in height and diameter.
Come to think of it there is an exception to every rule. If your grandfather planted the tree on his 21st birthday...