Theoretically Drowneds should only be able to spawn in Ocean biomes (and derivatives such as rivers) at light levels of 0 in 1.19. But I have a river in my world and although I placed glowstone to prevent spawning they still do spawn at a rate of around 507 per hour.
Are drowneds supposed to follow previous spawn rules of pre-1.19 of light level of 7 or less or is it a bug?