I'm curious if anyone is aware of the Point of Sale that's used for these fares?

When playing around with the OW tool, it seems to show availability based on the start location *of each leg *, not the start of the trip. So, for example an ex-OSL trip, I'd expect to be using Norway POS, but I see availability for a SIN-LHR leg in the OW booking tool when EF says 0D for Norway, but 1D for Singapore PoS.

I've seen this a few times while trying to force the routing I'm after.

Anyone know whether TA's or individual airlines apply their own local POS? Or a First departure point POS? Or if they also follow the OW tool with a point-of-departure-per-leg model?