it's the same list of authors, written in different formats

the first one is SURNAME, NAME separated by "and"

the second one is NAME SURNAME separated by commas

The second one is easier to read by humans, but the first one makes it clearer what is the surname (which would be ambiguous otherwise, when there are composite names). But then again, the first format breaks when someone has "and" in their name, which is not unheard of.

Why do they use "and"? Why not use an unambiguous joining token like `/`? This just feels like an abuse of informal language to produce fundamentally formal data.

As it stands, it certainly does not resemble readable or parseable english.

It’s BibTex format. It’s ancient, ubiquitous, very fussy, and reads badly for humans in some cases. But it’s what we’ve been using since the 1980s.

‘Better’ formats have been proposed but none have stuck nearly as well. It works, and there’s tooling for it.

It’s how the bibtex author field is defined. You don’t get free choice here. As far as I’m aware bibtex defines and as the separator

https://bibtex.eu/fields/author/

Yea but like... why? Typically you use human language operators to produce readable phrases, and this doesn't even approach readable english.

The person who designed it was solving primarily for lexical sorting of the author field, thought maybe having more than two authors was an edge case, and wanted the two author case to be a logical extension of the single author one?

The answer is probably who knows since we are talking about software from 1985 which was only updated once since 1988 to clarify its licensing

Infix composer "," has precedence over "and".

Names are ordered from general/family to specific/given.

That's just the formatting?

author = {surname 1, first name 1 and surname 2, first name 2 and ...}

"and" is the separator.