That should be: Passthrough drive controllers, and blacklist the controllers.
A HBA is a controller. A NVMe drive is its own PCI controler.
So if the Proxmox host has a -16i HBA (or a -8i and an expander) and slots for the three NVMe in the special vdev, you can just move your pool in, passing through and blacklisting the HBA and the three NVMe drives.
(Replace the three NVMe by three SATA SSDs, and the whole pool can hang on just the HBA.)
Useful dta point, showing a svdev at around 1% of total storage in this case of “mostly large files”.