Elite Four in Pokémon Brilliant Diamond & Shining Pearl for Nintendo Switch. Details the Elite Four, their tasks and their teams as well as their rematch teams
serebii.net
This page indicates
After you have defeated the Elite Four for a first time you'll be able to rebattle the Elite Four, this time with bigger and improved teams. The teams will then increase in level again and add more Pokémon from the National Pokédex.
While this is technically true there are additional requirements
To unlock initial rematch team- National Pokedex needed. (I attempted to rebattle prior to obtaining national Pokedex and got the same team)
To unlock secondary Rematch team- Seems to only be unlocked upon catching Heatran (though this may need to be tested as I'm not sure if just battling it is sufficient)
I'd probably also suggest splitting the separate rematches into separate sections rather than the merged forms they currently show.
Eg
Rematch 1
Aaron- Lists their 1st rematch team
Bertha-Lists their 1st rematch team
Flint- Lists their 1st rematch team
Lucian- Lists their 1st rematch team
Cynthia-Lists their 1st rematch team
then as a separate section
Rematch 2
Aaron- Lists their 2nd rematch team
Bertha-Lists their 2nd rematch team
Flint- Lists their 2nd rematch team
Lucian- Lists their 2nd rematch team
Cynthia-Lists their 2nd rematch team
It might even be sensible to split the elite 4 and the elite 4 rematches into separate page (similar to the gym leader and gym leader rematch pages)