gt table with an "unnkown" cell location created by the use of spanners and stub

I am trying to switch from Rmarkdown to a Quarto-document for some of my older Rmarkdown reports while rewriting, cleaning, shortening, and making the code more dynamic.
I am trying to recreate table E4 (the left side of the table is shown below as an example) using gt (I'm very happy someone created this package). The table is used for a research assessment (page 41 of this PDF ).
I had some trouble re-creating the table, so initially, I just created E4 without formatting, following the logic of the r package and marking "Starting Year" as part of the stub (because it identifies what each row represents, a cohort of year T). The original code used "Starting Year" as a column. My initial update of the code didn't work, so I defaulted to my more verbose code (which worked). Then I tried to style it based on my standard gt-theme (this specific table is a bit more complicated, so it creates a branch of the main gt-theme).
I am unable to identify a cell that is below the subtitle of my larger table (not visible in the example), and creates an empty cell that I cannot seem to fill with a colour, as I can't locate it (I thought it was part of the stub-head, but this is not the case).

I wonder if I'm just not looking at the correct place in the documentation to find its location. Or maybe I am misunderstanding the role of the stub (and I am using it wrong). Or that it is not part of the stub. I'm doing something wrong, I just don't know what. An earlier question was also created because I misunderstood the package function (so maybe that is the same case again).

Any help in colouring this cell is greatly appreciated.


library(gt)

df <- data.frame(
  year   = c("2020", "2021", "Total"),
  m   = c(10, 12, 22),
  f = c(8, 11, 19),
  total  = c(18, 23, 41)
)

gt(df, rowname_col = "year") %>%
  tab_stubhead(label = "Starting year") %>%

  # CHILD spanner (creates extra spanner row)
  tab_spanner(
    label   = "Enrolment (male / female)",
    columns = c(m, f)
  ) %>%

  # PARENT spanner
  tab_spanner(
    label   = "Enrolment",
    columns = c(m, f, total)
  ) %>%

  # Style everything that is officially targetable
  tab_style(
    style = cell_fill(color = "#001158"),
    locations = cells_column_spanners(spanners = everything())
  ) %>%
  tab_style(
    style = cell_text(color = "white", weight = "bold"),
    locations = cells_column_spanners(spanners = everything())
  ) %>%
  tab_style(
    style = cell_fill(color = "#001158"),
    locations = cells_column_labels()
  ) %>%
  tab_style(
    style = cell_text(color = "white", weight = "bold"),
    locations = cells_column_labels()
  ) %>%
  tab_style(
    style = cell_fill(color = "#001158"),
    locations = cells_stubhead()
  ) %>%
  tab_style(
    style = cell_text(color = "white", weight = "bold"),
    locations = cells_stubhead()
  )