The document you link uses unknown as a synonym for null. If you inserted the result of such a comparison into a table, the value inserted would be NULL.
create table #nulltest (a bit null);
insert into #nulltest(a) values (0),(1);
insert into #nulltest(a) values (null != null);However, that doesn't change things, I can't get any of these to parse:
insert into #nulltest(a) values (1 <> 0);
insert into #nulltest(a) values (null <> null);
insert into #nulltest(a) values (true and true);
insert into #nulltest(a) values (null and null);
The point of me asking is that it was my belief contrary to what was suggested, UNKNOWN is not the same as NULL and, crucially, does not evaluate as NULL.
Sql does not have this problem.