It has two more levels than CSV (which only has units and records) so no. And FS is file separator not field.

These were used for serial data sources, not just network but punch cards or drums or magnetic tapes. GS, RS and US were intended for databases on serial data sources, "group" is a modern-day table. Lammert Bies has more: https://www.lammertbies.nl/comm/info/ascii-characters.html

You can repurpose the final two (record and unit) for CSV, but that's not their original role, and you'll have to make sure they're never opened via user-controlled anything as these control codes are non-printable.

Even in the last few years I've seen FileMaker systems that used this set of ASCII characters to delimit fields in plaintext data exports. Initially baffling since I was expecting CSV, it seemed like a sensible choice once I figured out what they were doing.

Since it predates CSV, it wasn't an alternative to it: it was the original.

I suppose the Excel or 1-2-3 team either didn't know about the separator characters, or they did but then-current text editors weren't useful enough to do anything with them (and user-editability was important). It's a real shame: with a more integrated system, they could have added functionality to the editors to understand ASCII record encoding, and CSV need never have existed.

I use them whenever I can :)

Maybe a simple viewer would be nice.