In article , Sonny wrote:
You painted over joint compound and you painted over the paper of/on
the drywall, i.e., 2 different surfaces, hence the 2 different texture
results. The paper surface raised, a tad, when it was wet by the
paint, causing the difference in appearance/result. It is recommended
you compound over the whole of the drywall sheet,

Recommended by whom? You?

not just the taped
edges, so that the whole surface, to be painted, is uniform in/of
surface material. By applying compound over the whole of the drywall
(minimum extra work),

"Minimum extra work"? You've got to be kidding. Clearly, you've never actually
done that.

the painting results will be uniform.
Otherwise, to avoid the difference/results you describe, you would
need to apply at least 2 coats of primer. Applying the extra skin of
drywall compound is easier and cheaper, than applying the extra
primer.

What planet do you live on, where applying drywall compound is easier than
applying paint?