emacs describe-char missing info on unicode thumb up char

there are these unicode symbols

ok hand sign �� #x1f44c

thumb up �� #x1f44d
thumb down �� #x1f44e

when calling describe-char on them, it doesn't give their names.

is this a bug? does it happen to just few chars, or perhaps all chars outside basic multilingual plane? I know that many chars outside of BMP doesn't have this problem.

Xah ∑ http://xahlee.org/