Use of encrypting data in transit over a HTTPS connection

I find certain APIs (that provide sensitive information) using algorithms like ECDHE with X25519, on top of the already encrypted SSL connection. This compels us to use libraries like Tink (when we have to use it in Android Apps) that provides such algorithms, though the classes it provides us for using such algorithms is explicitly marked not to be used in production.

Is there any reason this could have use cases when transmitting sensitive information?