This jcmd option was added by the JVM team to analyze memory used by metaspace and is not useful to customers. Since then we've created better utilities. -Xlog:cds during -Xshare:dump is an example of a better utility that uses a newer better mechanism in the source code.
The output of this jcmd GC.class_stats is lengthy and not well suited to understanding memory used by metaspace objects, nor is it a GC specific facility. It also has some open bugs.
We should deprecate this in 14 and remove in 15.