bslib cards not resizing to fit content

the following code produces a vertical scroll bar on the data table inside the card, rather than scaling the card height to fit the content inside. here's a repex:

library(bslib)
library(DT)

card(
    card_header('why scroll if i said card_body_fill?'),
    card_body_fill(datatable(mtcars))
)

what's causing this? can it be fixed, or is it something that card_body_fill can't handle yet?