As far as I understand, they just mean to include it for everything, same as Go does:

“The microbenchmark suite will be co-located with the JDK source code in a single directory and, when built, will produce a single JAR file. Co-location will simplify adding and locating benchmarks during development. When running benchmarks, JMH provides powerful filtering capabilities that allow the user to run only the benchmarks that are currently of interest. The exact location remains to be determined.”

Solutions Architect @Depop, author of “Hands-on Design Patterns with Kotlin” book and “Web Development with Kotlin” course