Last I checked "OpenTracing-compatible" only went as far as using common terminology. Tbh I was a bit disappointed by this; has more been defined since? E.g. are there now shared schemas, APIs of sorts?
An analogy is SLF4J for Java logging. All libraries, etc use the same interface and the final user determines the backend: java.util, Logback. This makes sense if you have many authors of libraries with a cross-cutting concern.
This really makes OpenTracing half a dozen different standards, one per language, with common semantics.
Should it be about a wire protocol instead? Discussion at https://github.com/opentracing/specification/issues/34
There is an open issue about Envoy/linkerd/Istio support here: https://github.com/opentracing/specification/issues/86 (as well as in a number of other locations)
As an OpenTracing contributor, the core value prop still seems quite strong in that instrumentation of OSS dependencies is a massive pain point and should not be tracing-system-specific since it doesn't need to be. There is also value in common protocols and formats, and in that spirit there is interest in broadening scope to include those... though from seeing many companies adopt tracing tech, I haven't observed protocol compatibility as the main pain point or blocker.