render is fine. I just went through the install process and updated to the latest strapi version afterwards. I uploaded an image before and made an admin account. Both were persisted.
I think the confusion comes from a misunderstanding that I was thinking about in the beginning too: the content of the local development instance database wont be pushed to the server on deploy.
If you think about it makes sense that it is like this. Still a bit weird we need to register an admin account for the local dev instance. Maybe this is what adds to the confusion.
that you have these two things that look and feel so similar, but still are different and non connected.