Many built-in identifiers return bit masks. Why should this particular one be extended to offer a second way of getting the same information?
Most use properties - and properties make the code more readable.
I am not aware of other identifiers that use bit masks - my ignorance. Perhaps you can enlighten me.
I checked your code and it's using && instead of & it seems. All in all it looks like you are asking for the built-in identifier $dqwindow to return a $true/$false value if either of the bitwise comparison is true, which can be done in a custom alias easily then.
Yes, it was a typo and should have been & not &&. And yes it can clearly be done in a custom alias, because that was the example.
However, lots of things can be done using custom aliases - you can implement $left, $right and $mid as a custom alias using $asc and $chr and loops, but no one would suggest that would be a good way of doing it. Simpler examples would be $cr, $crlf, $lf; mirc.ini could be examined for $dccignore etc.
My point is that this would have been more consistent if implemented using properties in the first place, and retro-fitting it to be compatible both with the current implementation and consistent with the language by having properties would be a nice way of fixing this.
But I certainly accept that this is perhaps lower priority than other functionality and nice to have rather than essential.