Is this separate from that Heir to the Empire movie?
Yes, I believe it is. The Mandalorian and Grogu "belong" to Favreau (with Filoni advising). And I think Ahsoka and the Rebels crew are Filoni's and require Favreau's signoff.
Now you see why we call them "Favloni".
It is my strong belief that Favreau is very recently now in charge of Lucasfilm, and that Iger has made KK a figurehead while we wait for her contract to expire later this year. This means KK can no longer drive the business (like officially announce a Rey trilogy as "In Production"...it's not), but she is in a position to sabotage Favreau and steer things her way (like send Daisy Ridley and Sharmeen Obaid-Chinoy out there to "unofficially" make statements, or to influence Mando S3 and BoBF), after which Disney immediately announces something else officially.