Uppercase character predicate

Hello list,

I tried using the `char-uppercase-p' with the MATHEMATICAL FRAKTUR
CAPITAL A character (unicode #x1d504) but it evaluated to nil. I
peeked through `describe-char' to see how it comes up with the
description above (since I can use it to detect if a character is
capital) and I came up with this:

  (defun my/upcase-p (ch)
    "Check if CH is uppercase.

  Slower, but more accurate than `char-uppercase-p'."
    (string-match-p "CAPITAL"
                    (get-char-code-property ch 'name)))

This function works for my needs, but why doesn't `char-uppercase-p'
evaluate to true for this character?

-- 
Regards,
Nikolaos Chatzikonstantinou