It is not essential. It is a check to determine if the mount point is available. Usually is not a problem if you decide to use a mount point on a non volatile filesystem (like ext4, xfs, btrfs). Unfortunately you chose a volatile filesystem (tmpfs), which means the mount point is simply not available at boot.
I also believe, this is the reason you have a problem with dashes. Looks like systemd will automatically create a mount point if it contains a dash.
So, basically do not use /run for a static mount point. I will refer you to the second section of this tutorial “Structure and Content of a mount unit”.