What is cdk-erigon?

Why cdk needs an additional Ethereum client implementation?
I’d like to know the reasoning of cdk-erigon.

CDK already has cdk-validium-node which supports eth JSON-RPCs and zkevm RPCs.

I checked the article and actual source codes, but it just passes its request to sequencer when it receives Ethereum Txs. That means CDK provider must run Erigon + cdk-validium-node together which costs more than running just one cdk-validium-node.

Also there was a comment for performance in the article.

cdk-erigon uses 10x less disk space with +150x faster sync times on mainnet

I’d like to know some details for it. It says Erigon’s performance is only related with storing L1 (=Ethereum) states? That performance is not related with L2’s states?

Please let me know if I’m missing something.