Because indie doesn’t mean independent. It means small studios with low budgets, kinda, sometimes it doesn’t even mean that (See Clair Obscur winning Best debut indie game despite not being self-published nor being low budget).

The issue with equating indie to independent of publisher means that Cyberpunk 2077 is indie, Destiny 2 was indie for a while. The entire Monster Hunter franchise is indie. And technically Stardew Valley wasn’t indie at release. Neither is Terraria. So the technical definition of indie doesn’t fit the expected definition of indie.