I believe Sharp Shooter is referring to a rifle bore that is "seasoned" by the application of bore butter. They use the bore butter to protect the rifle against rusting and to facilitate shooting projectiles with a reduction in fowling and better accuracy, so the claim goes. The concern is if a petroleum based product was used to swab the fowling from the bore, this might also remove the seasoning effect of the bore butter.

In this case the correct swab solution would be a non petroleum based substance such as T/C #13, simple soap and water mixture, or an even more common fluid is your human saliva. You should still dry patch the barrel after the fowling swab.

If you were to smear additional bore butter into the barrel as a cleaning agent, I think the only effect would be is clogging the fire channel and producing a lot of misfires.

The patch for loading the ball is coated with bore butter. This in itself will pick up and remove fowling to a degree, when you load and shoot. As well as to continually season the bore.