Why is methyl chloride a primary alkyl halide?
Yes, you are correct. 

The IUPAC defines alkyl groups in the following manner:


  Univalent groups derived from alkanes by removal of a hydrogen atom from any carbon atom $\ce{–C_{$n$}H_{$2n+1$}}$. The groups derived by removal of a hydrogen atom from a terminal carbon atom of unbranched alkanes form a subclass of normal alkyl (n-alkyl) groups $\ce{H(CH2)_{$n$}}$. The groups $\ce{RCH2}$, $\ce{R2CH~(R \neq H)}$, and $\ce{R3C~(R \neq H)}$ are primary, secondary and tertiary alkyl groups, respectively.


Note that for primary alkyl groups hydrogen may be a remainder, i.e. $\ce{R $=$ H, Alkyl, Aryl}$, therefore any halogenoalkane with the structure $\ce{RH2C-X}$ is primary.