You only need mount points in each distro for partitions that you want to be able to access from that distro. If you don’t need access to your Arch system files from Debian, don’t mount the Arch partition in Debian.
But if you have a partition that you want to access from multiple distros, you don’t need to use the same mountpoint in each distro - just like a USB flash drive can be E:\ on one Windows computer and H:\ on another - that is just a name and the files on it are the same.