In this particular instance, Whitehurst isn't a board member, but per the press release[0] he is a "Special Advisor at Silver Lake". Silver Lake is one of Unity's largest shareholders (~10%) and Egon Durban is on the board.
EDIT: Also worth noting Silver Lake, along with Sequoia, committed an additional $1Bn into Unity at the time of the IronSource acquisition in the form of convertible notes with a conversion price of $48.89 / share[1], which is at a slight premium to the price at which Unity's stock traded then (7/15/2022) and at a meaningful discount to their current share price of $29.70 -- which supports the (admittedly speculative) argument that SLP's voice on that particular board is all the more prevalent today.
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[0]: https://www.businesswire.com/news/home/20231009494331/en/Uni... [1]: https://investors.unity.com/news/news-details/2022/Unity-Ann...