So basically, certain pokemon would have certain behaviours as wild and captured pokemon. For example, Wild Bug Pokemon would hang out in swarms or certain Pokemon like eevee would be very friendly and even try to walk up to the player.
special behaviors are in the same vein as special spawn conditions, this has been heavily considered and if it's up to me i'd say this would be awesome to have, to make the world feel extra alive. when the main features are finalized, i think it would be really nice to focus on making the world feel super cool by adding these small details