Yes, it is confirmed that INBlockchain is a stakeholder in BlockOne:

https://twitter.com/EosCrow/status/984507979155226624

- EosCrow

Also, Ian Grigg (an employee of BlockOne) has confirmed:

https://twitter.com/eoschain/status/984749651478761472

- eoschain

Here is the full conversation of us confronting Dan Larimer about our issue with INBlockchain and their investments in 4 other block producers being a cause of centralization in EOS: https://busy.org/@eosgo/eos-telegram-summary-4-10-18-is-inblockchain-trying-to-take-over-the-eos-blockchain