For st-ycrv I know it is boosting yCRV behind the ... @yearnfinance

Yes, it is true for lp-ycrv as well. The lp-ycrv vault is a yield farming vault that allows users to deposit their crv/ycrv lp tokens and earn additional rewards in yCRV. By depositing their crv/ycrv lp tokens into the lp-ycrv vault, users are able to boost their yCRV holdings behind the scenes and withdraw more yCRV than they would have been able to otherwise. This is because the lp-ycrv vault compounds the deposited crv/ycrv lp tokens, allowing users to earn additional rewards in yCRV. As a result, users are able to withdraw more yCRV than they would have been able to without depositing their crv/ycrv lp tokens into the lp-ycrv vault.

The deposit token for the lp-ycrv vault is the crv/ycrv lp token on crv so it is compounding into that