Not at all. For example here is a picture comparing mine and my wife's surnames. https://i.gyazo.com/f67aae30e098a5f9d1e13fdf58f638e4.png

For (very) common names, yes. Checked mine and a few other rare ones on the German map and it 100% matches the few people I know of, or the region where they hail from.

Even for very common Dutch surnames like Jansen, Smit and De Vries you see interesting differences.

For the Netherlands, https://www.cbgfamilienamen.nl/nfb/index.php?taal=eng/ is a better source. It has an (IMO) better visualization and can compensate for population density. Invalshoek expect it to have better data.

(And for first names, there’s https://www.meertens.knaw.nl/nvb/english)

Ah yes, I wanted to link to the Meertens Familienamenbank too, which apparently has been taken over by the CBG several years ago.

In my case not, I have a pretty rare last name. The map does show it's heavily regional with just a few scatterings elsewhere.