"custodial layer 2" is really a invention of term. lol Does it include CEXs, and Ethereum which issues wBTC custodied by BitGo?

I think this is a pyramid, not a layer. Imagine a manufacturing industry like cars, machinery, etc. Don't you think that ETF is a component made using bitcoin as raw material?

Saylor's layer theory is closer to processing and manufacturing up to the point where the product is delivered to the consumer.