Mostly correct. Fox owned the rights to make movies based on the Fantastic Four, so when Disney acquired Fox in 2019, Disney also acquired the rights to the X-Men and Fantastic Four (allowing those characters to rejoin the MCU). So while the prior Fantastic Four movies were mostly so Fox could keep hold of the rights, this one will be the first proper Marvel Studies Fantastic Four movie and thus fully in the Marvel Cinematic Universe.
Mostly correct. Fox owned the rights to make movies based on the Fantastic Four, so when Disney acquired Fox in 2019, Disney also acquired the rights to the X-Men and Fantastic Four (allowing those characters to rejoin the MCU). So while the prior Fantastic Four movies were mostly so Fox could keep hold of the rights, this one will be the first proper Marvel Studies Fantastic Four movie and thus fully in the Marvel Cinematic Universe.