It seems to me that the choice of relative pronoun in the second sentence hinges on a fine balance that tells us better not to use relative pronoun THAT in subject position in a non defining or non restrictive relative clause
A restrictive clause is an essential part of its sentence; if it were taken out of the sentence, the sentence’s meaning would change. Nonrestrictive clauses are just the opposite. Moreover, some people are squeamish to replace WHO with THAT when referring to people. Grammarly.com endorses the opinion.
https://www.google.com/url?q=https://learnenglish.britishcouncil.org/english-grammar/relative-pronouns-and-relative-clauses&sa tells us not to use THAT in such situations. In spoken English the usage is quite right but in written English, perhaps, not.