Hi,
There's a conditionalization for CMUCL in Apps/Listener/cmu-hacks.lisp to allow overriding package locks.
(#+CMU19C ext:without-package-locks #-CMU19C progn
It would be nice to get rid of the conditionalization. I doubt that ext:without-package-locks will be going away in future releases.
I'm pretty sure package locks were in all versions of cmucl 19 and some versions of 18.