How would they do that for just you and not change the price for everyone? Fares are published in GDS. Again, make comparisons based on fare class and fare class inventories to better understand what really is happening. Inventories are very dynamic, a particular fare class price is not (or wasn't until continuous pricing was implements, very recently -- but you and I will get the same price if searching at the same time).

As far as Google Flights finding cheaper prices, that is very true connecting itins because it does deeper searches. The airlines limit to fewer search tries. One trick is to search just oneways as the same number of searches are done for one-ways as roundtrips. (true for awards also)