Have you seen this self-review / retrospective ?
Specifically the section “Why do we do what we do?”
Also, here’s a link to a summary of my thoughts/links
from a previous topic thread that questions Zerodha’s priorities.
Specifically this bit 
When someone is NOT catering to you,
please understand that you are NOT the target audience.
There is no one-size-fits-all broker for everyones’ needs.
Presumably, Zerodha (technically Rainmatter) being a significant investor/owner of Sensibull, has better insights into Sensibull’s sustainability, and possibly a say into shaping/prioritizing Sensibull’s roadmap. Thus, it is maybe perceived as a lesser risk compared to typical 3rd-parties.