Not really, who spawned the container doesn’t matter too much as far as attack surface from within the container.
What matters more is what host uid/gid ranges are available to the container.
if two containers run with the same range then given the right set of kernel bugs, one container could become able to interact with the processes of another.
Preventing this doesn’t require different users though, only different lxc.idmap for each container and a large enough allocation to your lxc user so that it can give usable distinct maps to different containers.