Consider the following rule for FontConfig:

<match target="font">
<test compare="eq" name="family" qual="any" >
<string>ar pl kaitim big5</string>
<string>ar pl kaitim gb</string>
<string>ar pl zenkai uni</string>
<string>ar pl mingti2l big5</string>
<string>ar pl sungtil gb</string>
</test>
<test compare="less" name="pixelsize" qual="all" >
<double>18</double>
</test>
<edit mode="assign_replace" name="pixelsize" >
<double>18</double>
</edit>
</match>

The expected result is that text rendered with any of the above fonts, requesting a pixel size less than 18, uses a pixel size of 18 instead.

The actual result is that text rendered with any font requesting a pixel size less than 18, uses a pixel size of 18 instead.

Note that the problem does not occur with Gtk applications, where the rule is only applied to the matching fonts, not all fonts.