As an example, Exemplars are part of the metrics spec [1]. The official python library says metrics status is 'stable' [2]. But there's an approximately 2-year old issue with no work on it, titled 'Metrics: Add support for exemplars', where the latest update is that no work has begun [3]. Nothing at a top-level of the opentelemetry-python project indicates that the project does not implement everything in the metrics spec, so if you wanted to use that capability, you are apt to discover it relatively late.

[1] https://opentelemetry.io/docs/specs/otel/metrics/data-model/...

[2] https://github.com/open-telemetry/opentelemetry-python

[3] https://github.com/open-telemetry/opentelemetry-python/issue...