Grandparent comment is saying that Microsoft, Google, Apple could settle on a common set of open licence fonts and bundle them with the OS (and Linux distros / other OSS OSes could also do the same). Then web design & dev could rely on those fonts without having to locally serve them, or embed with Google fonts, etc. Noto could indeed be one of the bundled fonts in this alternate reality.

But no real incentive for any of those big players to do so, and disincentive for Google who gain surveillance data from font embeds as noted elsewhere in thread.

the same char in zh, tw, jp, kr might use the same unicode id but have different glyphs.

secondly, yes, but even google fonts strip most things from noto it serves because they want the fine grain data of each site/user is using wink wink.