It's not 100% clear to me from the video whether the new condensed, compressed and expanded font widths are intended to work across all four SF designs: default, rounded, serif and monospaced, or whether they will only work for the default design.
Is font width (condensed, compressed, expanded) intended to work across all designs?
In my own testing (hoping this Twitter link will work: https://twitter.com/geoffhackworth/status/1537786888626524162 ), I've found that the width only works for the default design. Attempting to vary the width of rounded has no effect, and attempting to vary the width of serif and monospace causes some font weights to actually return what looks like regular weight with the default design.