Granted cloudflare also does DDOS protection, and that makes sense for an API. For that you could do some DDOS protection without stripping TLS, but it can only protect against volumetric attacks like syn/ack floods and not against attacks that are establishing full TCP connections and overwhelming the app server. (rate limiting incoming connections can go a long way, but depending on details, it might still be enough to overwhelm the serving resources, your use case is up to you to understand).
At some level, it's like they become your edge router.