Yes. His parents lived in the US for a few years but did not stay in the US as permanent residents since they returned to China as was their intent to do at some point.
The act of having a place to live in the US makes you domiciled in the US.
Let's look up the legal definition of domiciled since you want to point out it is a legal term.
In re Garneau, 127 Fed. G77, 02 C. C. A. 403.In its ordinary acceptation, a person’s domicile is the place where he lives or has his home
Anderson v. Anderson, 42 Vt. 350, 1Am. Rep. 334. Domicile is but the established, fixed, permanent, or ordinary
dwelling-place or place of residence of a person, as distinguished from his temporary and transient, though actual, place of residence
Salem v. Lyme, 29 Conn. 74.Domicile is the place where a person has fixed his habitation and has a permanent residence, without any present intention of removing therefrom.
In other words, without evidence of intent to leave where they are living and move to another place within a short time frame, where they are living is their domicile.
A domicile is where a person is living and intends to live for the near future.