[css-fonts] Is "default caseless" matching really required for font names?

Per https://drafts.csswg.org/css-fonts-4/#localized-name-matching, font-family names are matched against names in font files using the "default caseless" matching algorithm defined by Unicode.

While the rest of CSS is either only ASCII case-insensitive (matching a-z to A-Z; otherwise case-sensitive) or fully case-sensitive (exact codepoint equality), this algorithm sits in a middle ground, allowing strings like "ſilver" to match "silver".

I expect that this algorithm is required due to legacy constraints with how font names work across platforms, but I'm filing this issue to ensure that's actually the case, and it's not just something somebody thought was reasonable at some point in the past, but could now be swapped out for the simpler ASCII case-insensitive matching.