[xsl] Is there any benefit to creating a variable and specifying as="xs:string"?

["Roger L Costello costello@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Hi Folks,

I have this xsl:param at the top of my XSLT program:

<xsl:param name="ICAO" />

Is there any benefit to adding this "as" clause:

<xsl:param name="ICAO" as="xs:string"/>

That "as" clause says the ICAO param is a string value. Well, everything is a
string. These are all strings -- '123', 'true', 'http://www.example.com',
'01101' -- all of which should not be used to populate the ICAO param. It
seems to me that adding the "as" clause provides zero benefits. In fact, it
has disadvantages: it makes the code more verbose, it requires more typing. Do
you agree that adding the "as" clause provides no benefits?

Bonus question: The value to populate the ICAO param should be a 4-letter,
uppercase value, such as KBOS. Is there anyway to express that
requirement/constraint in the "as" clause?

/Roger