Eli Zaretskii <eliz@gnu.org> writes:

>> The docstring also says this:
>> 
>>     If it is a list, all characters in the list are necessary for
>>     supporting SCRIPT.
>>     If it is a vector, one of the characters in the vector is necessary.
>
> So you want to require both upper- and lower-case variants?

As a mitigation against fonts like KpMath, yes.  See attached debugging
code, and subsequent patch/screenshot pairs.