Can you tell me if my understanding is correct:

Woman passes away in 2023.
She owned an IRA.
Her brother inherits 100%.

If he is older, he is an “eligible” designated beneficiary and can take RMDs over his LE.
Reasoning: because he is older, he is not more than 10 years younger

If he is not more than 10 years younger, he is an “eligible” designated beneficiary and can take RMDs over his LE.
He can be 1 year younger, 2 years younger, …… 10 years younger than his sister and qualify as a eligible DB.
If he is 10 years and 1 day younger than his sister, he is not an eligible DB and would be subject to the 10 year rule.

Thank you in advance for your help.