LanX> when scalar is applied to a list,

Here "list" is to be read as comma separated (literal) list. (see scalar comma separator)

Sorry for nitpicking but there is too much confusion. .

What confusion where (where is the confusion)? And how is this distinction important? In this case?

$ perl -MO=Deparse -wE "say scalar('a', 'e', 'i', 'o', 'u');"
Useless use of a constant ("a") in void context at -e line 1.
Useless use of a constant ("e") in void context at -e line 1.
Useless use of a constant ("i") in void context at -e line 1.
Useless use of a constant ("o") in void context at -e line 1.
BEGIN { $^W = 1; }
use feature 'current_sub', 'evalbytes', 'fc', 'say', 'state', 'switch'
+, 'unicode_strings', 'unicode_eval';
say scalar('???', '???', '???', '???', 'u');
-e syntax OK
[download]

I think its unimportant , esp in this case, a distinction without a difference ... list literal or literal list is not even in perlglossary

A different demo of the "null list"

## a literal list in list context
$ perl -le " print( qw/ a b c d / )"
abcd

## a literal list in scalar context
$ perl -le " print( scalar qw/ a b c d / )"
d

## a literal list in lvalue list context 
## a literal list in  list context  ( the left hand side list also hap
+pens to be an lvalue)
## a literal list in  list assignment (list context  )
$ perl -le " print( ( $q ) = qw/ a b c d / )"
a

## null list in scalar context counts, counting a list literal
$ perl -le " print( $q = () = qw/ a b c d / )"
4

## null list in scalar context counts, counting a "list"
$ perl -le " @f = qw/ a b c d /; print( $q = () = @f )"
4
## null list in scalar context counts
$ perl -le " print( scalar( () = qw/ a b c d / ) )"
4

## null list in list context discards (using literal list)
$ perl -le " print( () = qw/ a b c d / )"

## null list in list context discards (the array kind of list )
$ perl -le " @f = qw/ a b c d /; print( () = @f )"
[download]