Revealed column that must flag
Body copy at 1.6:1 against the page background. It is legible to the element pass only once the reveal wrapper has transitioned to full opacity, which is what a visitor scrolling the page actually sees.
A second paragraph set at 1.1 line-height, tight enough that the descenders of one line touch the ascenders of the next when the text wraps across the measure of this column.
Revealed column that must stay clean
The same amount of body copy at full contrast against the page background. It reveals on the same wrapper as the left column, so a pass that reads the post-reveal page sees it and finds nothing wrong with it.
A second paragraph at 1.6 line-height, the leading this size of text wants, wrapping across the same measure as the paragraph it is paired with on the other side of this fixture.