Q:

Looking for a word meaning "two things maximally mirror each other in symbolism"

I am looking for a word to describe the situation where two things are highly analogous, or parallel in symbolism, meaning, interpretation or purpose.
In the field of biology, we say that two candidate phylogenies (genetic descendency trees) are "maximally parsimonious" when the trees closely align. However the common English definition of parsimonious is "unwilling to spend money or use resources; stingy or frugal". So I don't think I can use that word outside the biological context.
I want to be able to say something along the lines of "This metaphor is highly parsimonious to [or with] reality" or "These two parables are highly parsimonious" or "Both readers had a parsimonious interpretation of the poem", but using a more appropriate word.
Candidates include the following (but I have a gut feeling there's a better word, and can't put my finger on it): harmonious, concordant, accordant, resonant, in tune.

A:

The term parsimonious is used by scientists and mathematicians in a figurative (lightly ironic) way, to express the key idea that the simplest explanation of data or phenomena is to be preferred.  This particularly applies to any underlying assumptions required by a theory.  The earliest expression of this idea in relatively modern times is probably William of Ockham (the 14th century Franciscan friar, more widely available through the hero of Umberto Ecco's novel the Name of the Rose, and its attendant movie, with 007 in the starring role!).  Ockham, or Occam, expressed a "principle of philosophy for the explanation of an occurrence" as Wikipaedia puts it:-

Suppose there exist two explanations for an occurrence.  The one that requires the smallest number of assumptions is usually correct.

The actual words attributed to Occam (but see https://simple.wikipedia.org/wiki/Occam%27s_razor) are:

Entia non multiplicanda sunt praeter necessitatem.
Entities should should not be multiplied beyond what is necessary.  I cannot resist pointing to the real gerundive, multiplicanda, not translateable into an '-ing' word, except, perhaps "entities are not for multiplying"!

Mathematicians, in the same way, try to reduce theorems to their most 'parsimonious' form.  It came to be called his lex parsimoniae, in an academic European world in which Latin was the universal language of scholarship.  Occam's law is sometimes called Occam's razor (used to shave off, it has been said Plato's beard - an implied criticism of Plato, who claimed that such ideas as justice, goodness and wisdom could only be understand by assuming that there exist real entities justice, goodness and wisdom which are palely represented ("imitated") in the physical world).
Your example is more like the way in which, for example, water follows the shortest available downhill distance, or films of detergent adopt the smallest area possible. A less potentially derogatory term might be

Economy or economical.

