LaTeX equations are rendered much smaller in PDF from xaringan slides, with partial_slides = TRUE

E.g. these slides:

---
title: "test"
output:
  xaringan::moon_reader:
    seal: false
    lib_dir: libs
    nature:
      highlightStyle: github
      highlightLines: true
      countIncrementalSlides: false
---

class: title-slide center middle inverse

# Title

---

### Slide 1 with formula $Q = 1 - P$

Formula is smaller here as well: $$Q = 1 - P$$

This is what I use to render the slides:

chromote::local_chrome_version(binary = "chrome-headless-shell")
renderthis::to_pdf("test.Rmd", partial_slides = TRUE)

It seems fine when I don't use partial_slides = TRUE.

Reproduce the issue from test.Rmd by running renderthis::to_pdf with partial_slides = TRUE, then compare it with the same document without that option. Trace the PDF rendering path involving chromote and the xaringan::moon_reader output. Done means LaTeX equations have consistent sizing in both rendering modes.