No, that banter triggered on my dwarf. There's one human-only inquisitor banter in Skyhold for Cassandra, and one extra line for the qunari inquisitor banter with Iron Bull with Cassandra. So I think things are pretty "fair."
Why did they think that odd numbers were lucky? And don't worry about not knowing about Thedas' calendar. They barely mention any of the dates, except in banters. I recently found out that Thedas days are Mon-Sun.
Historians are not too sure because so much of ancient literature has been lost. According to Plutarch, Romans thought that odd numbers were absolute, thus divine. We get lucky 7 from the Romans; September means 7 and was actually the seventh month in the old Julian calendar. 7 was thought by the Romans to be the perfect number, seven wonders etc.
Numa the second Roman king, who supposedly changed the calendar of Romulus to have 29 days in the 6 months with 30 days, is said to have ruled during the 8th century BC (the 700s lol). So the superstation dates back quite a long time.