Evaluation offer townhouse approx. 167m²

In my observation, proper bricks do not accumulate growth so quickly.

That is an unfounded hope. The "proper brick" arguably contains more nutrients for the growth. Keep in mind that the special construction supplements of the local papers are not researched by specialized editorial teams but are compiled from promotional press releases by the manufacturers. If you then also accept further half-knowledge by "telephone game," a variety of fortune-cookie insights emerge from the baker's flower. I believe you allow yourself to be too much misled in your effort to become an informed consumer before signing the construction contract.

There are surely more frequent cases where builders develop wishes after signing because they saw something elsewhere or whatever ... these addenda have nothing to do with sloppiness but simply arise later.

If builders do not participate in the sampling like adults, the providers are not to blame. The "process" of this princessly fickleness often costs more than the price difference of the nobler goods themselves. Such contractual changes are, by the way, not "addenda." Addenda are increases in effort or other augmentations of services and deliveries after acceptance of an offer.

I do not want to categorically exclude that we can talk about this.

Yes, I would consider that very sensible / purposeful. There are people whose profession it is to guide diffuse construction wishes to suitable implementers. This is no witchcraft; I have been dealing with it for forty years.