'x-create-frame' succeeds, but 'x-open-connection' fails with same display argument

[Herman]

Hi !

$ emacs --fg-daemon
$ emacsclient --eval "(terminal-list)"
(#<terminal 0 on initial_terminal>)
$ emacsclient --eval "(get-device-terminal nil)"
#<terminal 0 on initial_terminal>
$ emacsclient --eval "(x-display-list)"
nil
$ emacsclient --eval "(x-create-frame \`((display . ,(getenv \"DISPLAY\"))))"
#<frame *scratch* - GNU Emacs 0x55db73fd9c30>
$ emacsclient --eval "(terminal-list)"
(#<terminal 0 on initial_terminal> #<terminal 1 on :0.0>)
$ emacsclient --eval "(get-device-terminal nil)"
#<terminal 1 on :0.0>
$ emacsclient --eval "(x-display-list)"
(":0.0")
$ emacsclient --eval "(kill-emacs)"
$ emacs --fg-daemon
$ emacsclient --eval "(x-open-connection (getenv \"DISPLAY\"))"
nil
...
Debugger entered--Lisp error: (error "Display :0.0 does not exist")
  signal(error ("Display :0.0 does not exist"))
  error("Display %s does not exist" ":0.0")
  get-device-terminal(":0.0")
  frames-on-display-list(":0.0")
  font-setting-change-default-font(":0.0" nil)
  dynamic-setting-handle-config-changed-event((config-changed-event font-render 
":0.0"))
  funcall-interactively(dynamic-setting-handle-config-changed-event 
(config-changed-event font-render ":0.0"))
  call-interactively(dynamic-setting-handle-config-changed-event nil 
[(config-changed-event font-render ":0.0")])
  command-execute(dynamic-setting-handle-config-changed-event nil 
[(config-changed-event font-render ":0.0")] t)

Emacs 29.1.

/---
30.2 Multiple Terminals topic in Elisp manual says, 'x-open-connection' can be 
tested for communication with a given X display. What I have missed ?

Thank you in advance for your help !