I just noticed that all of the windows extra bosses have at least one spellcard in which they follow you in some way.
Flan, Suwako and Mokou have their survivals.
Ran and Yukari have Princess Tenko/Yukari's Spriting Away respectively.
Nue has Undefined Darkness.
And Koishi has part of her second survival card.
While we're on the subject of certain stage bosses carrying a theme, most stage 4 bosses have a gimmick changing their attack pattern, usually based on the player character.
You fight the character you aren't playing as in LLS
Yuki/Mai in MS
Patchy changes spellcards based on your shot type and character in EoSD
You fight a different Prismriver at the start of the fight depending on your player character in PCB
Reimu/Marisa again in IN
Satori changes spellcards based on shot type and character in SA
Aya and Murasa are boring.