I don't see it on my M3 MBP, nor my wife's M4 iMac. Both 15.3.1. But...
My 2019 iMac was showing up to six in Disk Utility with one or two mounted after reboot. I decided for this and other reasons to do a clean install (boot from USB installer, erase disk, install 15.3.1, no migration assistant). On first boot there was just one cryptex in Disk Utility and it is mounted. Has remained like this as I reinstall apps and so on. So a reinstall does not fix the issue, though it has reduced the number that I see in Disk Utility.
That is what I will do.