I am now officially confused.
I just completed testing all three options of that setting for version 3.7 of the plugin, and they all worked as intended. For each of these tests, I (1) changed the option, and (2) used Set regular prices
to reprice the variations. I tried each setting with the words “Test description” in the description, and without the additional text. I also tested each setting with and without pricing information already in the description.
Do NOT add pricing information to the description field.
The result was only the words “Test description” if that was there originally, and an empty description if there was no additional description text.
Add pricing information to the end of the existing description.
The result was the words “Test description” with the pricing information if the additional text was there originally, and only pricing information if there was no additional description text.
Overwrite the variation description with price information.
The result was that the words “Test description” were overwritten if present.
Note, also, that if there was no markup for a particular variation, the description field remained untouched.
I wish I could tell you what went wrong in your case, but I can not replicate the issue. ??