They way we personally interpret the meaning of a word affects its usage. In English, many younger people might use the word 'friend' when referring to someone they recently met and/or don't actually know a lot about. For me personally, that word is reserved for only a handful of people I really know well.
In Polish, technically, 'znajomy' should rather refer to an acquaintance, whereas 'przyjaciel' should refer to a closer friend. However, as I described above, different personal preferences make it hard to draw a strict line. I could even imagine that some people treat them as synonyms.
I'm not a native speaker, so please correct me if I'm wrong.
I am 84 now and have never in my life made that statement, it is my friend. It's always, this is my friend that we use. If I was telling someone what mwas done by either me or my friend, then it's, it my friend that did it.