I have pretty much never found anyone that recommends whole life policies outside of people that sell whole life policies.

Avoid this advisor most likely

I've seen one incredibly rich person do something similar with a whole life policy near the end of her life to get around estate taxes that actually kinda made sense as it was explained to me.

I would have to see the numbers on the specific policy in question, but I would be shocked if it's actually as good as the sales person claims. In general, I would stay pretty far away from whole life policies.

As someone who sells life insurance, I personally would stick to term policies. There are exceptions based on age/health etc to where a whole life policy can be better. As mentioned above, using it later in life to have the policy pay for estate taxes if your assets are in excess of 6million is a very wise move. If you have any questions just shoot me a text. 979-820-2271

I would read up on whole life. This guy covers most of the issues I have with it.

https://www.whitecoatinvestor.com/debunking-the-myths-of-whole-life-insurance/

But what's the opportunity cost of buying a term life policy and investing the difference in premiums between the 2 policies?

If you are at the point where you are considering purchasing a whole life policy to avoid estate taxes, I'd make sure to run the plan by a financial advisor with experience advising high net worth individuals. The one time I saw it make sense (I'm not a financial advisor) was with a 90 year old widow with a 9 figure NW from owning a business her late husband started ~60 years before.