Hmmm! The word "foreign" literally means

"1. of, from, in, or characteristic of a country or language other than one's own.

"a foreign language"

synonyms: overseas, exotic, distant, external, alien, nonnative

2. strange and unfamiliar."

So yeah, by the actual definition it is literally foreign to me. No one in my area that I've spent the last 25+ years in does this.

I am aware that people in different cultures and countries do it, though, and that literally makes it a "foreign concept" to me.

That's literally what that phrase means. That something is unfamiliar to the speaker.

Maybe re-learn English as it seems to be a "foreign concept" to you.