It seems like the digit arguments (digits, p_digits and ci_digits) are ignored for objects created by marginaleffects::hypotheses():
lm(mpg ~ wt, data = mtcars) |>
marginaleffects::hypotheses(hypothesis = "10*wt = 0") |>
parameters:::parameters(digits = 1)
#> # Fixed Effects
#>
#> Parameter | Estimate | SE | Statistic | p | S | 95% CI
#> ---------------------------------------------------------------------------
#> 10*wt = 0 | -53.44 | 5.59 | -9.56 | < .001 | 69.51 | [-64.40, -42.49]