The NAS boxes I can see either assume USB-C or don't seem to provide much clue to how to use an eSATA to connect between things. If they were easy to work with I think there would be a lot more 'use this box to house the disks and this cable to connect over to the computer' and sure, I'd use the single SATA at some saturated speed.
I live in ZFS. These box makers often assume you want to run their Raid card, and have optioned up 'to make it better' without understanding ZFS exists, uses its memory efficiently (ignore the 'not on less than 4GB' thing its highly specific to some time in history and de-dupe) and wants a dull-as-ditchwater HBA to talk to the drives. Or, worse yet, they embed the CPU and you buy their packaged solution with their suite of apps and their model of GUI. Like the NAS I moved off, which had a sparc CPU and ceased being able to run, aside from which it was locked to <2TB drives.
You're not wrong btw. I am just saying "no, the home NAS space isn't as easy as you say, if you want to run ZFS yourself" unless I have missed a key term to search for, getting standalone drive enclosures.
I can believe I am not the market. Mainly because very few SBCs have more than one SATA slot, even less more than 2 and many of the M.2 keyed sata cards are listed in a homebrew filestore page with "odd chip, drivers uncommon" -If I was the market I am sure by now, more of them would be mainstream and more web pages would say "sure: its easy!"