Plus, even if we disregard the Bell Beast thing, Lace definitely scales to Grandmother Silk’s durability and she’s fought in Act 2 with no special power-up beforehand, so it’d feel pretty arbitrary to suddenly stop the scaling right at her fight.
And if we went that route, we’d end up with Lace and the less hyped Act 3 bosses sitting in Tier 7, while Second Sentinel, First Sinner, Last Judge, and Phantom are down at like 9-B (Since the current 9-A feat scales to current Hornet) which is definitely not intended I feel.