I have two mains, and one of them is close to Elite Smash (I don't actually care about ES, since my preferred playstyle is free for alls, but that doesn't mean I avoid 1 v 1s (which I don't)). I find it funny how my two mains gain and lose different amounts of GSP even when they are very close (well they were close at one point but now there's a reasonable gap between them) on the ladder. For example, a few weeks ago both my mains were at around 4.8 mil GSP, yet when I win one match with one I only earn 35k but if I win another match with my other main, I earn 70k instead of 35k (and this is around the same GSP ballpark, my playtime and usage percentage with both are roughly equal). Weird. My King D3 is up at 5.15 mil GSP now, and it's really hard to be paired up with ppl with 5.1+ mil GSP nowadays (I usually get matched up with ppl between 4.3~5 mil GSP). I win one round, and I only get 6k~8k GSP (I believe most ppl in this range get 13~16k per win), but if I lose one round, I drop by 12k~16k. Conversely with Ike, I get 50k~60k per win at 4.9 mil GSP and lose ~80k to 100k per loss.
There's a wall in the system there. Basically, people in Elite Smash cannot match up against people outside of it. People outside of it cannot match up with people inside of it (or it's quite rare, not sure if it truly never happens but from my experience it seems to never happen). This is not a characteristic of a typical matchmaking system and is unique to Smash Ultimate, and it has some interesting side-effects.
If you're right below the threshold for getting into Elite Smash, you will be almost guaranteed to be fighting people with a lower Elo rating than you are. That's why you win few points, but lose many.
Take a look at the attached image. In my previous post, I stated two players who differ by 200 Elo rating will see a 3:1 win / loss rate against one another. Notice that the point the plot below crosses a 25%, or 75% win probability are at -200 and +200.
One interesting thing that can be observed here is that one may be able to deduce the actual Elo ratings from GSP by using the points gained / lost from multiple data points.
Let's say your GSP is right at 5.2 million, for example.
You lose a game against someone at 5.0 million GSP. You lose 25,000 GSP.
You again get to 5.2 million GSP and again match up against someone at 5.0 million GSP, but this time you win. You gain 11,000 GSP.
Take the ratio of the two. The game expects you to have a (25,000 / (25,000 + 11,000) = 69.44% chance of winning. Here's why, and here's where the numbers come from.
If your Elo ratings are a true reflection of your relative probability of beating this player, if you face off against each other an infinite number of times, your ratings will not change at all. They will stay entirely the same.
You have a 69.44% chance of winning. Every time you win, you receive 11,000 GSP. Every time you lose, you lose 25,000.
Perform 10000 matches.
You win 6944 of them, and lose 3056 of them.
You gain 6944*11000 GSP and lose 3056*25000 GSP.
You gain 76,384,000 GSP. You lose 76,400,000 GSP (they should be the same, but there's a bit of rounding error, since you really had a 69.44444444 repeating chance of winning).
Notice that you will stay at the same point forever if you keep winning 69.4% of the time.
Your Elo rating is thus, at 5.2 million, just by eyeballing the chart I posted, about 150 points higher than they are, or almost a standard deviation.
This is why the ratings and the GSP numbers behave as they do. All matchmaking systems do this.
I do think it's a bit silly that you can't pair up against ES members while not in it though, as having to sustain a win rate of nearly 3-1 or better to get in there is a bit annoying (and once you get in, you're almost guaranteed to fight a player with a higher Elo rating, of whom you have a <50% shot at winning against getting boot right back out!), but do keep in mind you are also fighting opponents with much lower Elo ratings than you have, and you have gotten skilled to a point where you can do that 2-1 or 3-1 win rate and succeed.
All the numbers here make sense if you look at your GSP, their GSP, the amount you won, the amount you lose (though getting a win / loss pair of data is a bit of a pain here since you'll be unlikely to match up with identical values for testing purposes).
In fact, if you want to get the best possible win / loss rate, your best bet is to deliberately stay right before Elite Smash and fight opponents who are guaranteed to be a lower Elo than you. When I was trying to build up to getting into Elite Smash, I was stuck right before it for several play sessions. My win rate was around 69% or so (which is between a 2:1 and 3:1 win ratio), pairing mostly up against upper 4m's or low 5m players. My example above may not actually be that far off from the true values.