I do not understand this problem - which we have indeed discussed quite often - unfortunately.
At the very beginning, we created a calculation with all the costs incurred. From the land, notary, house costs, kitchen, outdoor area, budget for furniture, budget for lamps, buffer, etc. That was a pretty long list and below it was a sum. Let's just assume that it was 500 K€.
Then we made a statement with our equity and looked at what we wanted to contribute from it. Let's also just assume 100 K€ here to stay with the example of the OP. => 100 K€ equity
So we needed 400 K€ from the bank - regardless of the form, whether with or without KfW => 400 K€ borrowed capital
I took this list with me to the bank meeting and asked the bank advisor to mark the items for which we should please use our equity and for which we need to submit invoices. => from my point of view a practical solution.
Due to the high equity ratio, the advisor said we should simply use our equity first and then gradually withdraw amounts while submitting the "larger" invoices (>10 K€). That would be enough. Sometimes 20 K€ were even paid out quasi blank.
But that depends on the bank. Therefore, my recommendation as described above. With the list as complete as possible to the advisor. He will then tell you what the respective bank "finances" and what you should rather pay from the equity.