The aliases sub-command reports hidden aliases, symbolic versions or hidden modules targeted by a non-hidden symbolic version.
$ cat mod/1.0
#%Module
$ cat mod/.2.0
#%Module
$ cat mod/.modulerc
#%Module
module-alias mod/.alias mod/1.0
module-version mod/1.0 .sym
module-version mod/.2.0 sym
$ module aliases
-------------------- Aliases ---------------------
mod/.alias -> mod/1.0
-------------------- Versions --------------------
mod/.sym -> mod/1.0
mod/sym -> mod/.2.0
All these elements should stay hidden as performed by the avail sub-command.