GSUB 'vrt2' feature is not a superset of the 'vert' feature.

### Prerequisites

* [x] Did you thoroughly search the [open](https://github.com/adobe-fonts/source-han-sans/issues) and [closed](https://github.com/adobe-fonts/source-han-sans/issues?q=is%3Aissue+is%3Aclosed) issues to avoid reporting a duplicate issue?
* [x] Did you go through the [official font readme file](https://github.com/adobe-fonts/source-han-sans/raw/release/SourceHanSansReadMe.pdf) to better understand the scope of the project, to include the *Known Issues* section at the very end?

### Description

The entry for Tag: 'vrt2' feature in the OpenType specification version 1.8.4 says "Note that these are a superset of the glyphs covered in the 'vert' table."
https://docs.microsoft.com/en-us/typography/opentype/spec/features_uz#tag-vrt2

However, if I understand correctly, in Source Han Sans and Source Han Serif, some glyphs (e.g. U+FF1A 'FULLWIDTH COLON' in Japanese) are covered by the 'vert' feature, but not by the 'vrt2' feature.
This means that 'vrt2' is not a superset of 'vert', but a subset.

I would like 'vrt2' to be a superset containing all the glyphs covered by 'vert' as the specification says.