I think there's a distinction - I would consider an "update" with new content to be something minor (such as BG3's recent epilogue content). "Free DLC" to me is a much more hefty addition, such as the Godmaster DLC for Hollow Knight.
(Disclaimer: I've not watched this trailer since I'm at work)
The Witcher 3 had 16 free dlc packs after release. I have no idea what they were or their distinction. Was definitely a marketing term for content updates that they can't sell because the content is so miniscule.