axisregistry build_fvar_instances produces nonfunctional nameIDs

[aaronbell]

Describe the issue

I am using the builder on a font project that does not include a Regular instance (Light - Medium - ExtraBold). As part of the builder process, fonttools.axisregistry's build_fvar_instances tool is run on the font source. This script deletes all the fvar table data, and replaces it with data that specifically aligns with the axisregistry standard.

However, as part of this process, it also adds the postscript name of the font to name table entry. For example:

`Light` -> `ChironSungHK-Light`
`Regular` -> `ChironSungHK-Regular`

etc.

The end result is that certain instances are no longer accessible. In the case of Chiron Sung HK, the Regular and ExtraLight instances cannot be accessed. This is likely due to their use in name ID 1/2 and 16/17.

I've verified that removing the postscript name corrects this problem.

The specific fix that I did locally, which solves this problem, is to comment out the line here:

            # inst.postscriptNameID = name_table.addName(
            #     f"{family_name}-{name}".replace(" ", "")
            # )

To Reproduce
You can test the fonts here: https://github.com/aaronbell/chiron-sung-hk-gf/tree/ce456afcb95bc8c1d065338779fb0da7dc3a71dd/fonts/variable

Expected behavior
Style names should be preserved AS IS without the postscript name attached, like so:

Additional context
Repros on MS Word for Mac 16.47

[aaronbell]

@m4rc1e It looks like you were the one who added the postscriptNameID to the instances, if you could comment.

[m4rc1e]

Thank you for the very comprehensive issue report!

We modelled our fvar instance names based on Adobe Source Sans. Do MS fonts even use them?

The end result is that certain instances are no longer accessible.

Which apps?

[aaronbell]

@m4rc1e the big one is MS Word for Mac. For some reason that app uses a concatenation of the fvar and stat table information to enumerate the instances and it appears that adding the postscript name causes MS Word for Mac to be unable to locate certain instances.

In the case of Chiron Sung HK, I could not select the Light or Regular instances, it would switch to the Medium instead.

I suspect it has to do with the use of name ID 17 / 2 for those specific instances versus the 200+ names.