I believe he was referring to the "income" not the "property". In Texas, income from separate property is community income (with rare exception). Yes, the gift amount and the inherited amount are separate, but any income earned on that separate property is community property in Texas.

The IRS warns of this in Publication 555

CAUTION:

Separate income. Generally, income from separate property is the separate income of the spouse (or the registered domestic partner) who owns the property. In Idaho, Louisiana, Texas, and Wisconsin, income from most separate property is community income.