I take all these stories with a grain of salt. You never know if these people are speaking the truth or if they have a personal vendetta. Joss Whedon worked on a lot of different projects since Buffy and Angel, so if it’s true, I’m sure other people will confirm or deny. Btw, he was hired in particular circumstances as he reworked that movie that began shooting with a different director. And they are actually doing another director’s cut for streaming only. But anyway that’s not an excuse if his behavior was really described as such.