这似乎是{recipes}中的一个错误。我已经打开了一个带有修复https://github.com/tidymodels/recipes/pull/1100的PR。
如果这对您来说是一个障碍，您可以使用remotes::install_github("tidymodels/recipes#1100")安装该特定分支。
使用该PR，您将得到以下结果

library(tidymodels)

rec <- recipe(mpg ~ disp, data = mtcars) |>
  step_spline_b(disp, degree = tune())

rs <- vfold_cv(mtcars) 

workflow() |>
  add_recipe(rec) |>
  add_model(linear_reg()) |>
  tune_grid(resamples=rs)
#> → A | warning: Some 'x' values beyond boundary knots may cause ill-conditioned basis
#>                functions.
#> There were issues with some computations   A: x1
#> There were issues with some computations   A: x5
#> There were issues with some computations   A: x8
#> 
#> # Tuning results
#> # 10-fold cross-validation 
#> # A tibble: 10 × 4
#>    splits         id     .metrics         .notes          
#>    <list>         <chr>  <list>           <list>          
#>  1 <split [28/4]> Fold01 <tibble [8 × 5]> <tibble [0 × 3]>
#>  2 <split [28/4]> Fold02 <tibble [8 × 5]> <tibble [0 × 3]>
#>  3 <split [29/3]> Fold03 <tibble [8 × 5]> <tibble [4 × 3]>
#>  4 <split [29/3]> Fold04 <tibble [8 × 5]> <tibble [0 × 3]>
#>  5 <split [29/3]> Fold05 <tibble [8 × 5]> <tibble [0 × 3]>
#>  6 <split [29/3]> Fold06 <tibble [8 × 5]> <tibble [0 × 3]>
#>  7 <split [29/3]> Fold07 <tibble [8 × 5]> <tibble [0 × 3]>
#>  8 <split [29/3]> Fold08 <tibble [8 × 5]> <tibble [0 × 3]>
#>  9 <split [29/3]> Fold09 <tibble [8 × 5]> <tibble [4 × 3]>
#> 10 <split [29/3]> Fold10 <tibble [8 × 5]> <tibble [0 × 3]>
#> 
#> There were issues with some computations:
#> 
#>   - Warning(s) x8: Some 'x' values beyond boundary knots may cause ill-conditioned b...
#> 
#> Run `show_notes(.Last.tune.result)` for more information.