I only finalized my financing 3 months after signing the contract. I already had an approval. For you, it will be a learning experience.
But it can also go wrong.... In my opinion, you should only do this if you know 1000% that the financing will work.
Even if it doesn't help you now. For this exact reason, I waived a combined land+house financing and accept that interest rates have been rising since the beginning of the year. In 4 months, the building permit will be ready, and then the house financing will start.
However, with your conclusion, you got a loan up to 0.5% cheaper than mine. That definitely amounts to more than €10,000-20,000 in interest savings on €400,000. Maybe it's better to look at it that way. Of course, assuming it doesn't ruin your financing right now.