Correct.
It’s only different in the way it’s attached. An external USB hard drive can NOT be hooked up to two computers at the same time. It must be attached to ONE of the two computers, and then the second computer can share it across the network. If the computer hosting the USB drives goes down, then NEITHER computer can access it. With the NAS; if one computer goes down, the other one carries on unhindered.
It remains to be seen about lag time, but it’s highly doubtful I’ll experience any. I use these NAS’s on my home network already, and they are QUICK and extremely reliable. I’ve had 6 of these NAS’s running 24x7 for a couple of years now, and never had even one crash.
If you think about lag though, I’ll be running at 1GB speeds between the computers and switch, with little else on the network. That’s MUCH faster than you could possibly get across USB 2, which many have successfully used with their external hard drives for years. I’ll be testing this theory out (and monitoring it) for a while before I’d ever use it live at a gig.
I haven’t mentioned how the Internet plays into this. I rarely need the Internet at the gigs I do. I can sometimes have one computer attached to the venue’s WiFi, or I have my own 4K router I can plug into my switch, which (in addition to Internet access) also provides WiFi access to the network I’m creating.