SQL Server order by with max rows in subquery -

the following query works postgresql , i'd know why doesn't work sql server 2016.

select * (values (1),(2)) a(a) union (   select * (values (1),(2)) a(a)   order 1 desc   offset 0 rows fetch first 1 rows ) order 1 desc offset 0 rows fetch first 1 rows 

can explain me why order not supported here?

funny following, way express this, works charm

select * (values (1),(2)) a(a) a.a in(   select * (values (1),(2)) a(a)   order 1 desc     offset 0 rows fetch first 1 rows ) order 1 desc offset 0 rows fetch first 1 rows 

is bug?

the query after union needs presented select, so:

select * (values (1),(2)) a(a) union select * ( select * (values (1),(2)) a(a) order 1 desc offset 0 rows fetch first 1 rows ) b order 1 desc offset 0 rows fetch first 1 rows