Can't explain that.
To my knowledge all the PTY-MDE flights regardless of equipment have J seats. I would think the AeroRepublica planes would fly domestically since, lets be real, those flights don't need J. I see LOTS of empty J seats on Avianca domestically. The flights that are full in J I generally presume are elite upgrades, because the fares themselves are a joke and I can't see anyone or any company justifying them. Combined with longer haul, sure fine but when MDE-BOG is like $80 and business is $300 not even providing a meal, you're essentially just paying to get off first.