Bullet hell shooters are deterministic. Mob behaviour in Silksong is random. It is entirely possible for a boss in Silksong to spawn several mobs that all do inconvenient attacks at once, boxing you in.

Some of the optional bosses in Silksong (e.g. Savage Beastfly, mentioned in the article) do have that issue: high damage + high health + spawning mobs with uncoordinated random movement. It makes for a prolonged sequence which is ultimately unlearnable but must still be performed perfectly.

It’s not that bad, you are still able to control your position and nudge the spawned enemies away, and force the boss to kill these enemies for you. And even if you get cornered here and there there’s plenty of time and space in this fight to heal back.