Why is lua require("which-key").show("M", {mode = "n", auto = true}) not generated for M keymap using mini.surround?

[TheFunctionalGuy]

Hello,

is there any specific reason that the lua require("which-key").show("*", {mode = "*", auto = true}) is not automatically generated if I bind something to capital M?

Example using mini.surround triggering this behavior:

{
  "echasnovski/mini.surround",
  opts = {
    mappings = {
      add = "Ma",
      delete = "Md",
      find = "Mf",
      find_left = "MF",
      highlight = "Mh",
      replace = "Mr",
      update_n_lines = "Mn",
    },
  }
}

Expected behavior when looking at the keymaps:
x M * <Cmd>lua require("which-key").show("M", {mode = "v", auto = true})<CR> and
n M * <Cmd>lua require("which-key").show("M", {mode = "n", auto = true})<CR> have been generated

Actual behavior when looking at the keymaps:
only x M * <Cmd>lua require("which-key").show("M", {mode = "v", auto = true})<CR> has been generated

This works when for example using:

{
  "echasnovski/mini.surround",
  opts = {
    mappings = {
      add = "Za",
      delete = "Zd",
      find = "Zf",
      find_left = "ZF",
      highlight = "Zh",
      replace = "Zr",
      update_n_lines = "Zn",
    },
  }
}

I am not sure whether this is a bug in which-key or in mini.surround.
That's why I'm asking here for an assessment here.

Cheers