It is extremely rude of him not to say hello.
And extremely rude and undermining of your DH not to prompt him to do it, and to make a big deal out of it if he doesn't say it.
Hi, bye, please and thank you are absolutely non-negotiable for me, whoever you are, wherever you are, and pretty-much whatever age you are.
Saying hello is a social ice-breaker, an acknowledgement of the other person being there in the same space. If there's another conversation to be had later, especially a difficult one, it is immeasurably helpful to have said hello earlier.
One of the biggest complaints and causes of a breakdown of relationships in the workplace is people 'not even saying hello' to each other. The lad is nearly 16 FGS. Assuming no additional needs, this is a perfectly reasonable expectation to have.
I don't care if it's a tad uncomfortable for little darlings like this, they need to buck up and show some manners. And your DH needs to support you, in what is also your own home.