Water connection installed incorrectly - Right to correction from the general contractor?

As long as the water drains and the basin works, no defect can be seen. Buy yourself a pedestal and install it, then nothing will be visible anymore. Although it is somewhat questionable in terms of taste now, some people like it.

Well, if you hang a designer siphon under a DIY store 0815 washbasin, I do have my doubts

I do not understand the unpleasant undertone in this thread - just because the OP paid a different "net" service, as he could describe it, it does not mean that this service was invoiced accordingly.

On the topic: The pictures show an installation that I would not like to accept in this form. What matters is what you discussed with your installer. Was he aware of your expectations? If yes: have it redone. If no: find the next best solution and learn to make the next agreements more precise.

I have agreed with my craftsmen that we do not negotiate. We neither negotiate discounts (good for the craftsman) nor reductions in service quality (good for the client). The regular agreements on the construction site go into detail when it matters to us and are well documented. Invoices are paid promptly in full. Errors (so far very few) are immediately and fully corrected. It costs more than average and I expect more than average. Everyone knows that and everyone benefits. The emotional situation is relaxed and positive for all involved.

As long as the water drains and the basin functions, no defect can be detected. Buy yourself a half-pedestal and install it, then nothing will be visible anymore. Although this is somewhat questionable in terms of taste, some people like it.

That is a matter of agreement. In our bathroom, a stone basin will be placed on an antique table in front of a Sicis glass mosaic wall. The black wall fittings and siphon are carefully selected. Everything is discussed and marked out. I would not accept a half centimeter deviation.

My statement was explicitly related to this issue in this thread. You can also lay tiles with the help of GPS. No problem at all, for those who are willing to pay. The same goes for your approach; if it is agreed beforehand that there is zero tolerance, then that is just how it is.

However, this case is completely different.

Laying tiles with the help of GPS

Funny!

How different this case is, I cannot say, as I do not know the arrangements. However, the assumption is quite likely that they are missing. Then it would be: learn from it and coordinate better next time.