Merriam-Webster’s Dictionary of English Usage (1989): “The notion that that should not be used to refer to persons is without foundation; such use is entirely standard.” It traces the interchangeability back centuries and deems both correct in standard English.
Garner’s Modern English Usage (5th Edition, 2022): Classifies the restriction against “that” for people as a “skunked term” (a debated usage in flux), but affirms both are valid, with “who” more formal.
"Standard", as it is used here, simply means we have debased it for such a long time, it's okay to ignore it. I don't think it should be ignored.
Garner’s Modern English Usage (5th Edition, 2022): Classifies the restriction against “that” for people as a “skunked term” (a debated usage in flux), but affirms both are valid, with “who” more formal.
If "that" is used to refer to people and it is a "skunked term", why not use the "non-skunked" form?