How does "instantiate" differ from "reify"?

In 2004, I asked Merriam-Webster the following question. Emily Brewster from the editorial department replied as follows.

Q: Instantiate means “to represent (an abstraction) by a concrete instance”; heroes instantiate ideals. Reify means “to regard (something abstract) as a material or concrete thing.” How do the two terms differ?

A: The genus terms in the two definitions in question differ significantly; the answer to question lies in that difference.

Note the first definitions of “regard” and “represent”:

regard: to consider and appraise usually from a particular point of view

represent: to bring clearly before the mind: present

Using these definitions, we can redefine reify as “to consider and appraise (something abstract) as a material or concrete thing,” and redefine instantiate as to “bring clearly before the mind (an abstraction) by a concrete instance.”

In this way, trees at various stages of development instantiate growth, but if you reify growth, you imagine or consider it as something that can be held or touched.