Oh cool, I didn't know about this. I guess they tend to publish more infrastructure-oriented papers, which is understandable, but I wish there was more in general about the developer APIs that they enable and how they benefit productivity from a product engineer's point of view.
Lead author on the deletion paper here. Thanks for the feedback! I agree it would be cool to talk about the Ent APIs some more; they have a lot of obvious and less-obvious benefits. (For example, we are only able to add deletion constraints to Ents as described in the paper because the Ent specification language is expressive enough to do it.)
[1] https://engineering.fb.com/2020/08/12/security/delf/