Why don't all OpenType features work in fonts served via the API?

Fonts being served using the CSS API do not have the same OT features as their downloadable counterparts (`fonts.google.com/download?family=FAMILY` ZIPs).

If I extract TTFs from the CSS:
```
/* cyrillic-ext */
@font-face {
font-family: 'Montserrat';
font-style: normal;
font-weight: 400;
src: local('Montserrat Regular'), local('Montserrat-Regular'), url(https://fonts.gstatic.com/s/montserrat/v12/rBHvpRWBkgyW99dXT88n7wsYbbCjybiHxArTLjt7FRU.woff2) format('woff2');
unicode-range: U+0460-052F, U+20B4, U+2DE0-2DFF, U+A640-A69F;
}
/* cyrillic */
@font-face {
font-family: 'Montserrat';
font-style: normal;
font-weight: 400;
src: local('Montserrat Regular'), local('Montserrat-Regular'), url(https://fonts.gstatic.com/s/montserrat/v12/NX1NravqaXESu9fFv7KuqgsYbbCjybiHxArTLjt7FRU.woff2) format('woff2');
unicode-range: U+0400-045F, U+0490-0491, U+04B0-04B1, U+2116;
}
/* vietnamese */
@font-face {
font-family: 'Montserrat';
font-style: normal;
font-weight: 400;
src: local('Montserrat Regular'), local('Montserrat-Regular'), url(https://fonts.gstatic.com/s/montserrat/v12/SKK6Nusyv8QPNMtI4j9J2wsYbbCjybiHxArTLjt7FRU.woff2) format('woff2');
unicode-range: U+0102-0103, U+1EA0-1EF9, U+20AB;
}
/* latin-ext */
@font-face {
font-family: 'Montserrat';
font-style: normal;
font-weight: 400;
src: local('Montserrat Regular'), local('Montserrat-Regular'), url(https://fonts.gstatic.com/s/montserrat/v12/gFXtEMCp1m_YzxsBpKl68gsYbbCjybiHxArTLjt7FRU.woff2) format('woff2');
unicode-range: U+0100-024F, U+1E00-1EFF, U+20A0-20AB, U+20AD-20CF, U+2C60-2C7F, U+A720-A7FF;
}
/* latin */
@font-face {
font-family: 'Montserrat';
font-style: normal;
font-weight: 400;
src: local('Montserrat Regular'), local('Montserrat-Regular'), url(https://fonts.gstatic.com/s/montserrat/v12/zhcz-_WihjSQC0oHJ9TCYAzyDMXhdD8sAj6OAJTFsBI.woff2) format('woff2');
unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2212, U+2215;
}
```

They only contain dnom, frac, liga, numr OT Features. If you download the family from GoogleFonts, they contain a ton more.

I'm guessing our settings for pyftsubset are removing features we deem unnecessary?