I mean, has any linguist noticed this?

Yes.

Also, I think in German it's very common to string together words like that to form longer words. Are there more languages with that characteristic?

Yes. All of them.

Can the same argument be supported at the word-level also?

Here it depends what you mean by "the word-level". "Words" are commonly taken to be compositionally opaque. Compound expressions are not compositionally opaque and are not "words" in this sense.