Meaning of strong

As a result of action 1489, I am taking a close look at the text of section
7.5:

https://rawgit.com/w3c/aria/ACTION-1489/aria/aria.html#host_general_conflict

 

My first set of questions from this section are about this paragraph
describing strong native semantics.

 

"Host languages may document features that cannot be overridden with
WAI-ARIA (these are called "strong native semantics"). These can be features
that have implicit WAI-ARIA semantics, as well as features where the
processing would be uncertain if the semantics were changed with WAI-ARIA.
Conformance checkers may signal an error or warning when a WAI-ARIA role is
used on elements with strong native semantics, but as described above, user
agents must still use the value of the semantic of the WAI-ARIA role when
exposing the element to accessibility APIs."

 

If I understand this paragraph, in the event that an author specifies an
ARIA role for an HTML element that has strong native semantics, a
conformance checker may call out an error. However, a browser must ignore
theHTML semantics and use the ARIA semantics.

 

Questions:

1.       Is my understanding correct?

2.       If the browser must respect the ARIA, isn't the first sentence
incorrect where it uses the word "cannot". Shouldn't "cannot" be replaced
with "should not"? 

3.       What is an example? Could we include one in the text?

4.       Why do we call this "strong" native semantics if they have no
effect on the way user agents and assistive technologies behave? What is
"strong" about this? It seems more like they are "preferred" native
semantics.

 

Matt King