A point spawner spawns `n` quantity of pokemon. Distortions spawn packs (groups) of pokemon, therefore `n` is not 1. For fixed/static encounters that need a correlation, they are spawned w/ quantity of 1.
What's the point? Making sure things are legal. The amount of logic needed to do a "smart" reroll of every single PIDIV for every single encounter is more effort than it is worth -- it is not a simple PIDIV correlation, there can be other values correlated like OT Gender/Version (CHANNEL Jirachi), Height/Weight/Scale (raids), original Nature, ability... just use the encounter database to regenerate from a template.