Really? Is that so? I thought there are only 3 and 98 ;) What does it take to get 100? No mobile contracts? No overdraft? 1 million in the [TG]?
Let's leave Schufa as a company and its quality aside. What they do have there, however, is a lot of data. We probably agree on that.
By the way, the million in the Tagesgeld does not affect the score at all, except insofar as it may reflect other existing behavior. And that is the most important thing in the whole matter. It is pure statistics and a pure probability consideration.
Thus, it is one piece of information among several.
So let's look at the probability of default (PD). This is internationally standardized and always considered over a one-year period and is the counterpart to the probability of fulfillment (in our case here, Schufa score).
Statistically speaking, there is a default within 50 years.
No one can tell you whether it will be in the first or last year. Nor does it say anything about how high the default amount will be (keyword collateral) and how much can still be recovered (recovery rate).
If you now have the opportunity to grant a loan to 50 people each for one year for 1,000 euros (unsecured) and you are statistically sure that you will not get your money back from one of these 50 people, then you have to charge 2% interest from each to cover your risk. Then you have (on average) not earned even 1 cent yet.