New construction: Connection & cabling Internet + TV

Of course, you "normally" don't do that. It's not about costs, but a solution approach in case the OP ends up missing exactly 1 port at the end of the day. Then it actually doesn't hurt, not every device needs GBit LAN. By the way, almost all GCs we have checked build it that way as standard.

What is the point of splitting the number of ports? If I feed a double socket with one cable, I still need 2 ports at the patch panel and switch. This cable splitting hasn't been done for quite some time now. A GC who still does this today deserves to be "tarred and feathered"!!! Still, always talk to the GC and communicate clearly what you want.

If I connect a double socket with one cable, I still need 2 ports on the patch panel and switch.

um, yes, mistake in my thinking

I hope the master electrician understands everything the way I want it.
How do you assess the workload in my case? Quite unusual or rather standard for today's single-family house?
How long does an electrician approximately need for wiring, patching, connecting, installing sockets, etc.?

In crowds, I would say unfortunately not yet a standard. A normal electrician should be able to properly and fully terminate a [Netzwerkdose].

Are you building with a general contractor (GU) or individual contracts?
With individual contracts, I see no problem at all.
With a general contractor, you never know. But it is certainly not standard.
But for an electrician, it is an easy task.
Provide the network cabinet, patch panel, etc.
They should give you a plan showing which cable is terminated where and a protocol where each connection has been measured through.
At my sister's place (bad general contractor, now insolvent) we had to measure everything to find out which port corresponded to which socket. It also turned out that two sockets were poorly terminated and only ran at 100 MBit. After I re-terminated them, everything was as it should be.

I hope the master electrician understands everything the way I want it
How do you assess the workload in my case? Is it already unusual or rather standard for today's single-family house?
How long does an electrician approximately need for wiring, patching, connecting, installing sockets, etc.?

When it comes to pulling cables itself, there is no difference between 3x1.5 and Ethernet. The rest depends on your construction company or the contracting. Just ask beforehand, with us double sockets in three rooms and a patch panel in the basement are standard, the rest for an additional charge...