Both first and last author names appear in references regardless of bibliography style

[stsievert]

\bibliographystyle{abbrvnat} has only shows the author's first initial and last name: https://www.overleaf.com/learn/latex/Natbib_bibliography_styles

However, even if I select this bibliography style, both author names are always shown.

Here's a minimal working example:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}

\usepackage[square, numbers]{natbib}
\bibliographystyle{abbrvnat}

\begin{document}
Here are some hyperparameter optimization papers:
\cite{li2016hyperband}.

\cite{sievert2019better}

\bibliography{refs}{}
\bibliographystyle{plain}

\end{document}

# refs.bib
@InProceedings{ sievert2019better,
  author    = { {S}cott {S}ievert and {T}om {A}ugspurger and {M}atthew {R}ocklin },
  title     = { {B}etter and faster hyperparameter optimization with {D}ask },
  booktitle = { {P}roceedings of the 18th {P}ython in {S}cience {C}onference },
  pages     = { 118 - 125 },
  year      = { 2019 },
  editor    = { {C}hris {C}alloway and {D}avid {L}ippa and {D}illon {N}iederhut and {D}avid {S}hupe },
  doi       = { 10.25080/Majora-7ddc1dd1-011 }
}

@article{li2016hyperband,
  title={Hyperband: A novel bandit-based approach to hyperparameter optimization},
  author={Li, Lisha and Jamieson, Kevin and DeSalvo, Giulia and Rostamizadeh, Afshin and Talwalkar, Ameet},
  journal={arXiv preprint arXiv:1603.06560},
  year={2016}
}

Output:

[stsievert]

The references also look significantly different when [square, numbers] isn't passed to natbib:

[stsievert]

The braces in the Bibtex file are causing this.

If I change the refs.bib file to remove the braces in the author field, I get the correct output:

The changes I made were in refs.bib and are

-  author    = { {S}cott {S}ievert and {T}om {A}ugspurger and {M}atthew {R}ocklin },
+  author    = { Scott Sievert and Tom Augspurger and Matthew Rocklin },

[deniederhut]

🤔

I'm guessing from the commit history that bibtex was messing with the capitalization of people's names, but this was a bit before my time. @stefanv do remember the context around https://github.com/scipy-conference/scipy_proceedings/commit/8e6a9960f0e2214dd59a46aa4f604bbbee6c7ad9?