Column widths not porting to LaTeX

[leachandrew]

It seems that specified column widths are not porting to longtable in LaTeX when knitting to PDF from gt.

Here's my sample code:

grades_table<-tribble(
  ~Minimum, ~Maximum, ~Grade,
  #--|--|----
  90,100,"A+",
  85,89.99,"A",
  80,84.99,"A-"
  )
gt_test<-grades_table %>% gt()%>%
tab_header(
    title = md("Grade mapping table"),
    subtitle = "Percentages will correspond to letter grades as follows:"
  ) %>%
      cols_width(
    starts_with("M") ~ px(200),
    everything() ~ px(200)
  )%>% cols_align(align = "center")%>%
  tab_source_note(md("NB: In the event that overall percentages are lower than expected, your grade may end up above those posted here, but will not end up below."))%>% as_latex()

gt_test

When I look at the generated latex code, the cols_width specifications don't come through:

\captionsetup[table]{labelformat=empty,skip=1pt}
\begin{longtable}{ccc}
\caption*{
\large Grade mapping table\\ 
\small Percentages will correspond to letter grades as follows:\\ 
} \\ 
\toprule
Minimum & Maximum & Grade \\ 
\midrule
90 & 100.00 & A+ \\ 
85 & 89.99 & A \\ 
80 & 84.99 & A- \\ 
\bottomrule
\end{longtable}
\begin{minipage}{\linewidth}
NB: In the event that overall percentages are lower than expected, your grade may end up above those posted here, but will not end up below.\\ 
\end{minipage}

It seems that longtable is a bit fussy about alignments and widths, but it seems like the \begin{longtable} line should be something like:
\begin{longtable}{p{200px}p{200px}p{200px}}