DOB of 1/6/1951 means that 2023 is his first distribution calendar year and his required beginning date is 4/1/2024. If he takes a distribution during 2021 or 2022, it would not be subject to any RMD requirements, since neither 2021 or 2022 are a distribution calendar year. Of course, if he rolls it over to an IRA, he will have to start RMDs from the IRA by 4/1/2024.
As an aside, you should be aware that whether someone is a 5% owner for RMD purposes is determined solely with respect to the year they turn 72 (formerly 70½, although the regs have not been updated yet). Meaning that if he sold the business in 2022 and he was not a 5% owner during 2023, he would not be subject to RMDs from the plan until he actually retired. RMDs have to start from an IRA regardless of whether you are retired or not.