The same happens on Juju 3.1.6:
➜ ~ juju exec --unit easyrsa/0 -- leader-set my.test=value ➜ ~ juju exec --unit easyrsa/0 -- leader-get my.test value ➜ ~ juju exec --unit easyrsa/0 -- leader-set my.test= ➜ ~ juju exec --unit easyrsa/0 -- leader-get my.test value
➜ ~ juju exec --unit easyrsa/0 -- leader-set my-test=value ➜ ~ juju exec --unit easyrsa/0 -- leader-get my-test value ➜ ~ juju exec --unit easyrsa/0 -- leader-set my-test= ➜ ~ juju exec --unit easyrsa/0 -- leader-get my-test
The same happens on Juju 3.1.6:
➜ ~ juju exec --unit easyrsa/0 -- leader-set my.test=value
➜ ~ juju exec --unit easyrsa/0 -- leader-get my.test
value
➜ ~ juju exec --unit easyrsa/0 -- leader-set my.test=
➜ ~ juju exec --unit easyrsa/0 -- leader-get my.test
value
➜ ~ juju exec --unit easyrsa/0 -- leader-set my-test=value
➜ ~ juju exec --unit easyrsa/0 -- leader-get my-test
value
➜ ~ juju exec --unit easyrsa/0 -- leader-set my-test=
➜ ~ juju exec --unit easyrsa/0 -- leader-get my-test