You can have a perfectly stable, solid, and accurate position fix with 6 satellites just as you can with 9,14, or 20. And it goes both ways. You can have a crappy, useless, drifting position position fix with 6 satellites just as you can with 9, 14, or 20. Put another way, just because you "only have 6 satellites" doesn't mean your position fix is any worse than it would be with more satellites. And just because you have 20 satellites, doesn't mean your position fix will be better.
There is a lot that goes into determining if a position fix is accurate and usable for a drone. Number satellites is one of many factors that goes into it. And it is really one of the least important factors of them all, and has very little direct correlation to accuracy. It's a LOT more complicated and strict than your Google Maps or the GPS in your car, which makes assumptions that don't matter.
Where a very high satellite count is useful, is it's ability to cope with satellites moving in and out of view as the drone moves around. The more you have, the more you can lose. This isn't making a "better signal" or making it more accurate. It makes it more redundant.