ordereless-flex filtering is not orderless

[mhlr]

M-x apr cus does not retrieve customize-apropos.
when using fussy-20221010.2026/ installed from melpa

I have

(use-package fussy
  :ensure t
  :custom
  (fussy-compare-same-score-fn 'fussy-histlen->strlen<)
  (fussy-max-limit-preferred-candidate-fn 'fussy-histlen->strlen<)
  (fussy-filter-fn 'fussy-filter-orderless-flex)
  (fussy-default-regex-fn 'fussy-pattern-flex-2)
  :config
  (push 'fussy completion-styles)
  (setq
   completion-category-defaults nil
   completion-category-overrides nil))

M-x apr cus works if instead I use orderless with

(use-package orderless
  :ensure t
  :custom
  (orderless-matching-styles '(orderless-flex orderless-regexp orderless-literal))
  (completion-styles '(orderless basic))
  )