More or less true. If you think of where tour tongue is when making an l or an r sound, the Japanese and Chinese equivalent tends to be somewhere in the middle of that. Which is a sound that is similar to either but is neither.

So it isn't that I'd say the phoneme is alien, it's just the east Asian phoneme doesn't exist in English and it only has one variation, where in English there's two different phonemes. If you think about it the L and R sounds are actually very similar mechanically, but since native English speakers grow up with a language that differentiates them the brain picks up on it as necessary information for determining meaning. Someone growing up speaking Japanese or Chinese it doesn't really matter if you get sloppy with the pronunciation of your L or R since the phoneme in those languages is singular and the differentiation is not important towards meaning so native speakers of those languages don't get the same mental awareness of the change.

On the flip side both Chinese and Japanese have some tonal qualities in vowel tones that are important towards meaning, far more pronounced in Chinese (most Japanese curriculum will not mention the two tones in Japanese since it will scare off beginners and isn't really important as the correct meaning can be interpreted by context, as well as tonalities varying by dialect) .

If you listen to the Chinese tones side by side you can definitely make them out and hear the difference, but it's very hard to reproduce especially in conversation if you're growing up in a language that doesn't consider tones to be integral to meaning. Same for Japanese or Chinese speakers with L or R, they understand the difference but it's hard to use when their language simply considers both to be equivalent.