Rectangling data: special cases

df_unnamed_paired |> unnest_longer(c(y, z))

## # A tibble: 5 × 3
##   x     y     z    
##   <chr> <chr> <chr>
## 1 a     a1    A1   
## 2 a     a2    A2   
## 3 b     b1    B1   
## 4 b     b2    B2   
## 5 b     b3    B3