How do I revert a Disk Utility volume name from 'q' to the original naming convention?

if what you want to accomplish is seeing a more recognizable Volume-name,

remember that the advanced symmetry of MacOS allows to the re-name ANY Icon, anywhere, without causing any system distress whatsoever.

Specifically, select the top-level of the Drive in Finder, GetInfo to see all fields, and enter a new name of the drive.

if you insist on seeing EVERY component Inside the drive data structures named with those recognizable names, that may take making a complete backup, "erasing all content and settings" in Recovery, and re-installing MacOS and migrating your files back from your backups.

<< Is it “Macintosh HD”? >>

yes, that is the name provided on the factory-created Volume.

But as you found out, you are free to choose a name that is more meaningful to you.

In my example, I am using MacPro silver tower with four internal bays, and naming its several different bootable drives Macintosh HD is not helpful to me, so I used a different convention that works better for me.

FYI, you may need to manually change each item currently named "q" to "Macintosh HD". It is also possible changing the name of the top most item in the "Volume Group" will automatically rename the other two "q" objects.

Just right-click or Control-click on the name within Disk Utility & select "Rename". The interface is terrible and you may not notice the text cursor within the name on the right pane of Disk Utility.

Unfortunately every version of macOS since 10.15 handles the naming & renaming of objects within Disk Utility differently. I don't think I've ever tried renaming them on Sequoia.