でもって>>593リンクの中に並び順が保証されてるわけじゃないと書いてある

so, while I cannot imagine
select rownum, x.* from (select ... order by ... ) x
not being sorted by rownum (by the order by), it is permitted to not be sorted.

... Why would it be permitted not to be sorted? ...
because there is no order by on the outer query. that is why.

https://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:1137689100346245972