Sure, I also said that too. I have never heard it said but when asked 'how to say x' or 'do you speak x' this often also implies the knowledge of the diction. I.e, the word or character used to communicate. I have no doubt that peopldo not say this in modern China,  colloquially.

It has the meaning of living person, and is also grammatically correct, but with dialects, you just say things a certain way. 生人 might be correct in written form, but we do not say that when speaking the language, at least not when speaking Madarin or Cantonese. I'm fluent in both dialects, so I know. But different dialects say things differently, so there might be a dialect that call "living person" 生人; however, I only know Mandarin and Cantonese, so I don't know which dialect would say that.

gnilma

https://www.zdic.net/hans/%E7%94%9F%E4%BA%BA

ideasfromtheedge

Learn Chinese with Sensei #2: 自由人

cryotosensei

You don't say 生人 in Mandarin, you might in other dialects. 活人 is the correct term for living person in Mandarin. If it's specifically a man, then it's 活男人.