Custom font sets doesn't fully work

[Yuan Fu]

This is what I did (in emacs -q)

(create-fontset-from-fontset-spec
 (font-xlfd-name
  (font-spec :registry "fontset-lunamono")))

(set-fontset-font "fontset-lunamono"
                  'latin (font-spec :family "SF Mono"))
(set-fontset-font "fontset-lunamono"
                  'han (font-spec :family "Source Han Sans"))

(set-face-attribute 'default nil :font "fontset-lunamono" :height 130)

Now I expect Latin characters show in SF Mono, and Han characters show in 
Source Han Sans. However, only Latin characters work right, Han characters 
doesn’t use Source Han Sans.

If I use fontset-default instead:

(set-fontset-font "fontset-default"
                  'latin (font-spec :family "SF Mono"))
(set-fontset-font "fontset-default"
                  'han (font-spec :family "Source Han Sans”))

Both Latin and Han characters show in the right fonts. What gives?

Yuan