Accidental kerning pair in Sans: standard (tabular) 1 and 7

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Problem description

Today, I got a message from a friend on Twitter:

in the desktop Recursive Sans fonts, when numbers are set to tabular lining, it seems the 7 still exhibits proportional metrics

Expected behavior

Tabular figures should basically be monospace – they should all have exactly the same width, with no kerning.

Screenshots

Cause

This is actually seemingly due to errant kerning in the 17 pair, rather than the 7 having a different width. Note that in Font Goggles, the 1 is shown to have different widths when used next to 7 than 8 – that is how Font Goggles shows the result of kerning. This is the case across weights (All weights in Recursive share the same kerning.)

Recursive Sans has tabular figures active by default, and only a pnum (proportional numbers) OpenType feature as an option (not a tabular numbers feature). With pnum, things look as expected:

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Perhaps a clearer way to prove that this is a kerning issue:

Kapture.2021-08-10.at.16.30.53.mp4

I might also explore making the default 1 a little wider at the bottom right, or maybe even added a contextual alternate ... I can see what kerning was added to that pair, because it there is a pretty big visual gap in that pair, when they have no kerning.