I believe those are 2 different topics. The decision to increase ETH exposure was suggested by the community and approved on a recent PTIP.
I can clarify why we prefer adding POOL/ETH liquidity instead of POOL/USDC liquidity though. First, we’ve seen that POOL has more correlation with ETH than USDC. This allows us to deploy tighter ranges and thus improve liquidity and slippage. Moreover, thinking about the hyperstructure, we believe that ETH has better liquidity than USDC with other tokens that might be added as yield sources. This will allow the liquidators to avoid an extra step when converting the yield into POOL, which will save the AMM fees of that extra trade.
Regarding the fees, you can take a look at our recent post where some numbers where shared: Ethereum Mainnet POL - Review.
You can also take a look at live numbers in poolexplorer: Pool Together V4
The POL on mainnet was deployed on the 22nd of September 2022.