What is `tinytex.verbose = TRUE` supposed to do?

I'm moving from MacTeX to TinyTeX, and for a legacy project I've found that I need to use LuaLaTeX and Biber for typesetting and references. Consequently I'm typesetting using tinytex::latexmk('talk.tex', engine = 'lualatex', bib_engine = 'biber'). I'm trying to track down a missing reference warning, and can't find where (if anywhere) the biber messages are being logged. Based on some other responses to issues in this repo, I thought options(tinytex.verbose = TRUE) might be helpful. Basically I expected it to show me the lua and biber messages as they're generated, similar to the "typesetting" windows in TeX Shop and similar software. But it doesn't seem to change the output of the latexmk() call in any way — all I see is the same minimal output:

[1] "talk.pdf"
Warning message:
LaTeX Warning: There were undefined references.
Package biblatex Warning: Please rerun LaTeX.
(biblatex)                Page breaks have changed.

So, what is tinytex.verbose = TRUE supposed to do?

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Start with the tinytex::latexmk() call described in the issue and investigate what options(tinytex.verbose = TRUE) is intended to expose when using LuaLaTeX and Biber. Compare the command's output with the expected LuaLaTeX and Biber messages; done means the option's behavior is clarified or the missing output is addressed.