Error: Metadata VDEV must be the same type as the data VDEV

[KevinM]

I have a new Supermicro box that I'd like to set up with a metadata VDEV. The data VDEVs are RAIDZ2, so to maintain the same 2-drive redundancy per VDEV I'd like to use a 3-way mirror with NVMe drives for the metadata VDEV. However when I went to create the pool I got a red error message like "metadata VDEV must be the same type as the data VDEV." There is an override button however. So my question is, is this some sort of TrueNAS middleware thing, or is it really bad practice to have RAIDZ2 VDEVs with a mirrored metadata VDEV?