I suspect that the term "conventional usage" is also relative and varies on a country and/or regional basis.
Here in the US, and perhaps elsewhere, other terms are always (frequently?) mentioned in a specific order: "Salt and pepper", "Neither here nor there", "Ins and outs", "Ups and downs" ... to name a few.
I rarely, if ever, see "Pepper and salt", "Neither there nor here", " Outs and ins", "Downs and ups".
Thanks for dropping in.
HBB in Phoenix, Arizona Nikonian Team Member
Photography is a journey with no conceivable destination.