Thanks for the nice question with plenty of knowledge involved, but I've got it just because none of the above made sense for me, and the explanation is not 100% correct as even if we have 5 Null values in the table, the operator EXCEPT will act as explained in BOL:

EXCEPT returns any distinct values from the left query that are not also found on the right query.

So it will never ever return 5 rows, if NULL values come to play, there will be just one row with NULL value in it.

declare @t table (numericColumn int)

insert into @t values (-10)

insert into @t values (-9)

insert into @t values (-8)

insert into @t values (-7)

insert into @t values (-6)

insert into @t values (-5)

insert into @t values (-4)

insert into @t values (-3)

insert into @t values (-2)

insert into @t values (-1)

insert into @t values (0)

insert into @t values (1)

insert into @t values (2)

insert into @t values (3)

insert into @t values (4)

insert into @t values (5)

insert into @t values (6)

insert into @t values (null)

insert into @t values (null)

insert into @t values (null)

insert into @t values (null)

insert into @t values (null)

SELECT *

FROM @t

EXCEPT

SELECT *

FROM @t

WHERE NOT (NumericColumn BETWEEN -1 AND -10);

Cheers