I have made piglins initiate combat with hoglins and wither skeletons, and it seems to happen less than 2% of the time for each victory. This is made a lot rarer considering that piglins don't fight hoglins very often. I bet I could explore the Nether and raid enough bastions to get all netherite gear without mining for ancient debris before I see a piglin dance.

Note that me using wither skeletons to test this may have made it seem rarer than it actually was.