/usr/local subdirectories allowed?

I'm currently having some conflicted doubts about the /usr/local folder according to the standard. In our application, we currently store our read-only application files in /usr/local/. While going through the [Filesystem Hierarchy Standard](https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s09.html) it noted that no other directories may be in /usr/local other than those listed. Another [user on Stack Overflow](https://stackoverflow.com/a/34166003/9398242) quoted a text specifying that /usr/local/ is supposed to be used, but I'm unable to find this part in the FHS. Other examples I've seen on my machine are /usr/local/mysql and /usr/local/percona. Are these simply not in line with the standard? Should we be switching to /usr/local/share/?