It isn't who makes it as much as who set the standards for it! There are many companies that blend the oil for retailers to put their label on. We have a NAPA right next door and they refer me to their other blends for my cars for quality.
Here in NY for hydraulic fluid we do recommend the Hytran oils from Case because of the amount of water they can absorb. We have varied temps thru out the year which gives us a lot of condensation in gear cases and that oil can absorb more then the other oils we tested against. This saves pump starvation when things are frozen.