I am also not aware of this. If this is true than I think a lot of Rootstock supporters would change their minds on the project. Can you please add a source?

At the same time, we decided to contribute back to the Bitcoin network by providing its miners the opportunity to merge-mine RSK and use all their installed capacity to validate decentralized smart contracts. In return, they will protect the RSK blockchain. As a result, every time a person or a corporation runs a smart contract on RSK, 80% of the fuel paid goes to the miners and the remaining 20% to RSK Labs, so we can continue the development of the open source platform.