Maybe. My experience with booking international flights at various schedules from “tomorrow” to “1 year in advance” is that airlines don’t give a discount for booking far in advance, past about one week out it’s all the same. I haven’t investigated thoroughly, though.

I find 2 and 4 weeks to be the magic cutoff points for discounts but maybe I'm just seeing a pattern where none exists.

Also plausible. Given that even when you book a year in advance you are booking a specific flight time, I don’t see many big efficiency wins for airlines here.

Trade and tariff negotiations between countries comes into play, too. It was a while ago now, but I remember looking at a round trip flight to Sydney from the US. The same two planes, in different order (round to the US from Sydney) was half the price. I hadn't planned a year in advance, so I couldn't pull the trick mentioned above.

Possibly but my flights to SF from Europe are routinely half the price for a round trip the other direction on the same dates/airline.

I'm sure they compared the prices for SFO -> XYZ -> SFO with XYZ -> SFO -> XYZ for the same dates.