Question on metalized holes of multilayers PCB

[GGMM]

Hello,
Question on metalized holes of multilayer PCBs.

May you confirm that a metal hole on a multilayer PCB is only a single connexion between 2 layers. (Where more, but it is the same "electrical" connection like on schématic?)
Extreme example: if you have a pcb with 8 layers, you will never have extreme connection between layers 1-2,3-4,5-6,7-8.  --->so 4 # connexions in only one hole.
Which means that if you put a wire and weld it completely into this hole, you don’t change anything if it’s in good condition.
I think you have understood my question.

cdt

[RoGeorge]

If you fill a PCB hole with solder, you won't alter the already existing connection between layers, if that's your concern.  It's safe to fill a metalized hole with solder.

Metalisation covers the walls of the hole entirely, but only those layer that have to be connected together are bring in contact with the copper deposited inside the hole.  The other copper layers (those that have to stay isolated from a hole's metalisation) are kept away from that hole, so they wont make electrical contact with the metalisation.

[GGMM]

Thanks for the answer
If we dig a little deeper, we see that it is a fairly complex process to metallize the holes.
For your information:

https://www.raypcb.com/6-main-processes-for-making-high-quality-pcb-plated-though-holes-pth/

cdt