Processing of the role attribute not clearly defined

[zcorpan]

For the role attribute, https://w3c.github.io/aria/#introroles says

User agents MUST use the first token in the sequence of tokens in the role attribute value that matches the name of any non-abstract WAI-ARIA role. The following steps will correctly identify the applicable WAI-ARIA role:

The above only has one MUST requirement; the second sentence and the list below are statements of fact. I think the first sentence should be removed, and the second sentence should say "MUST".

1. Use the rules of the host language to detect that an element has a role attribute and to identify the attribute value string for it.

What does this mean? Is it applying the requirements from html-aam for HTML?

2. Separate the attribute value string for that attribute into a sequence of whitespace-free substrings by separating on whitespace.

What does "whitespace" mean? Should this use https://infra.spec.whatwg.org/#split-on-ascii-whitespace ?

3. Compare the substrings to all the names of the non-abstract WAI-ARIA roles. Case-sensitivity of the comparison inherits from the case-sensitivity of the host language.

What does this mean? HTML has some attribute values case-sensitive, some ASCII case-insensitive.

4. Use the first such substring in textual order that matches the name of a non-abstract WAI-ARIA role.

(This step seems clear enough.)

[joanmarie]

To me, the enumerated steps seem redundant to the "User agents MUST" statement.