[css-will-change] treatment of upper case values

How should an upper case will-change value like "TRANSFORM" be serialized in specified and computed values? Should it have the same effect as a lower case value?

Firefox:
Values like "TRANSFORM" are serialized with their case preserved in specified and computed values.
Case is ignored when matching against property names, e.g. "TRANSFORM" creates a containing block, just like "transform".
Values that are not a case-insensitive match for a property name are still preserved in specified and computed values.

Chrome:
Values like "TRANSFORM" are serialized in lower case in specified and computed values.
Case is ignored when matching against property names, e.g. "TRANSFORM" creates a containing block, just like "transform".
Values that are not a case-insensitive match for a property name are rejected, i.e. specified value serializes as empty string and computed value is "auto".

Safari:
Values like "TRANSFORM" are serialized in lower case in specified and computed values.
Values that are not a case-insensitive match for a property name have their case preserved in the specified value serialization, but the computed value is "auto".

Edge:
The will-change property is not supported.

The <custom-ident> spec mentions

Such identifiers are fully case-sensitive (meaning they’re compared by codepoint), even in the ASCII range (e.g. example and EXAMPLE are two different, unrelated user-defined identifiers).

The will-change spec mentions

Indicates that the author expects to animate or change the property with the given name on the element in the near future.

Should will-change explicitly mention a case-insensitive match between the custom-ident and propery name?

Read the will-change specification and the CSS Values 4 custom-ident definition, then compare the Firefox, Chrome, and Safari behavior described in the issue. Determine whether case-insensitive matching and serialization of property names should be specified explicitly; done means the specification wording resolves the observed differences.