If I’m not mistaken, the point of the front midarm is primarily to keep the front axle from walking under the Jeep during extreme droop. With a short arm and 12” shocks the control arms can reach a dangerously steep angle at droop. With a midarm that problem is solved. The 3 link is primarily a packaging fix as well since I’m sure Johnny joints would support full travel even if there was a 4th link. There’s just not enough room for a 4th midarm link correct?
Partly yes. IMO any shock longer than 26.5" in the stock mount allows the front to droop too far with the stock arm length. Longer arms help with that, reduce roll steer and improve caster angle (or pinion angle through travel depending on link orientation). Three link is typically use for both packaging as has been mentioned and for less axle bind since we typically have a track bar adding constraint to the axle.