[css-values-4] Restrictions on UA-default viewport units (unprefixed v*) #6454

In #4329 we added three sets of more explicit viewport units--the small, large, and dynamic viewport units sv*, lv*, and dv*--and left the unprefixed viewport units to be UA-defined.

The current wording of the spec is:

The UA-default viewport-percentage units (v*) are defined with respect to a UA-defined UA-default viewport size, which for any given document should be equivalent to the large viewport size, small viewport size, or some intermediary size.

Are there any other restrictions we should be adding to the UA's choices here (besides svh <= vh <= lvh)?

For example, the sv* and lv* units are explicitly not dynamic (this is their whole purpose). Should v* be likewise restricted to a non-dynamic interpretation, so that components using them are not resized as one scrolls?