I agree with you. My mom is very into plants but she never calls her pots of mini trees penjing. But I guess there's the language aspect of the word usage as well: 'penjing' (literally pot of scenery) sounds very formal like written language, not very colloquial. It would sound like an advertising word as if from a production video or a market. Whereas the Japanese counterpart is regarded as an established high art/profession (which is common in Japanese society).