Regarding the building savings contract: here the bank advisor must tell you, in addition to the amounts, how high the follow-up fee is (often 1%) and the annual processing costs (often between 10 and 30€).
As you have already correctly understood, after the allocation (in your case after 11 years) you will repay the bank loan of 232,000€ through the building savings contract. You have already saved a little over 80,000€, the rest you now have to pay back to the building savings contract. This is of course not interest-free, but like with the annuity loan, the sum is interest-bearing. The advantage of the building savings contract is that you already know today the interest rate of the entire sum. This is quite significant, because if, for example, 5% is stated there, it would only be worthwhile if in 11 years the interest rates are significantly above 5%. After the allocation, there is also a premium on top that has to be paid additionally. Also something in the four-digit range. Only with these figures can you make a comparison. Based on your numbers, I had calculated an interest rate of about 3.5%. That is not really good.
Regarding the interest rates, the bank advisor has misled you somewhat. The interest rates apply only to the bank loan over the first 11 years and the KFW loan over the 20 years of interest certainty. The remaining sum is of course not interest-free and the interest on the building savings loan he also omitted. So several tens of thousands of euros come on top of that again. From my point of view, the offer is therefore not serious because he did not tell you important things. I would not want to conclude there. If he then comes to you with the argument that you do not have to accept the allocation if the interest rates in 11 years are lower than agreed in the building savings contract, then he is basically right, but then you pay considerably more for the 11 years than with a pure annuity loan.
My opinion: it is certainly possible to set up a good financing with a building savings contract. But it always depends on the details. If you do not understand the construct exactly, you should keep your hands off it. You should always know in your financing what options you have in which situation. If you do not even understand the system, it makes no sense. What happens if you want to reduce the rate? What if you want to make special repayments (in which of the 3 building blocks)? Can I extend or shorten the financing?