When lxd is upgraded, it may break a running lxd until it is restarted. That's not a big issue if you are upgrading only lxd and you know that you have to restarted.

However, if it gets upgraded in a larger set, like when doing an unattended @world update, you won't know to restart lxd until you're done upgrading.

So, it would be better if the ebuild itself detected whether lxd is running and restart it.