Um, I don't know what information you're getting but this is easily Googleable eg [1]:
> The tax basis of property acquired by a beneficiary from someone who dies is ordinarily the property's fair market value at the date of the decedent's death.
[1]: https://www.fidelity.com/learning-center/personal-finance/wh...
Do you have a reference for this?
Any sort of gift or inheritance transfers the cost basis as far as I know.