For me "non-standardized' means there is not one recognized standard, this does not mean that things are completely unstable, nor that there are no traditions of what character is used for what word that have been passed down for many generations.
/As I stated/, for a decent number of syllable-morphemes (probably the /majority/ of Cheung-Bauer entries shouldn't be considered active or passive knowledge), native speakers will have no clue how to write them, and the array of characters to chose from (if C&B is used for a forced-choice task), or often a good portion of the array, either appears unsatisfactory to them or is seen as okay but previously unknown. Native speakers have no problem approximating these syllables otherwise if pressed, but, yes, things for those syllables are not that stable and if there are stable traditions, they might not be well-known except for a low percentage of C&B entries – definitely less than half, but I don't want to commit to a specific number.
Nonetheless, both type and token frequency of such syllable-morphemes are low.
Stephan