At the moment, core doesn't discriminate attribute/property types by HTML element, instead, adding them to a huge singular interface. Compat has recently added most per-element interfaces for types, though the HTML elements all still use the singular interface from core. Strangely, core has ended up with MathML element interfaces though.

We should make this more consistent. Per-element types shouldn't impact maintainability for the better or worse really, but would appeal to many who want stricter types for their elements (see #4202). Moving all the attribute types over to core and attaching InstrinsicElements up to them seems like a good move at this point, though there are some risks of type breakages in the ecosystem.