These two are completely independent things. I e the creation of the language resources and running the engine and keyboard, so no need for the log. There simply seems to be an asymmetry in the runtime setup when using the default language resources (en, fr, nl) and others, the latter are completely restored each time and this equals to removal if there are no files to restore for that language.
It should probably by symmetrical behavior, but you can argue for both behaviors. The language resource developer can easily make the extra steps of putting the resources in /usr/share/okboard/, while the end user will probably want any new resources installed to be used rather than the old one in ~/.local/share/okboard/. But a simple test if there are no resources for the language installed in /usr/share/okboard/ one just keep the local one will probably be good, but would add to complexity.