Trying to understand Motte and Bailey, but the examples I've seen are rather lacking

I think this is more about the strong argument, weak argument style, though I may be wrong. Correct me if so.

Let A and B be two persons who disagree on X

Let Y be something A and B both agree upon

A asserts X and uses Y as evidence for X

B contradicts X

A asserts Y is true therefore X is true

So, in an example,

Let X be crystals meet the definition of life

Let Y be crystals grow and that they respond to external stimuli

A: Crystals meet the definition of life because they grow and respond to external stimuli

B: Crystals are not alive

A: But they grow and respond to external stimuli

The issue of course being that the definition of life was never established, it is merely asserted that Y is evidence of X.

Am I following down the right path? I do not find the articles I've pulled up on Motte and Bailey to be very concise in their explanation of the tactic.