Question about haloalkanes
While homologous series are a very nice thing for teachers to quiz students about, they practically don’t matter to modern lab chemists. Sure, we all know that methanol, ethanol and propan-1-ol form a series and that a $\ce{CH2}$ unit is added when going from one to the next but in terms of actual lab properties the three are different enough to be remembered individually. As for most synthetic applications, linear molecules (the only ones for which a homologous series makes some sense) are not really any target of relevance so they won’t be thought of.

That said, I see nothing against applying a term that works well for many functional groups (e.g. $\ce{OH}$ or $\ce{NH2}$) to another functional group ($\ce{Cl}$) so the only argument against calling them one is ‘my teacher said so and it’s important that I know that in the upcoming exam’.