Steady to his purpose, he scarcely spoke ten words to her through the whole of Saturday, and though they were at one time left by themselves for half an hour, he adhered most conscientiously to his book, and would not even look at her.

I am afraid I’ve read this paragraph differently. The ten words he did speak must have been the usual greetings etc… so I suspect that he covered the etiquette aspect of the day. Furthermore, they were left alone which suggest that they were in the room with other people doing whatever (reading and needlework, I suspect) when other people left so no additional greeting was required. I don’t get impression that his manners were at fault, but I am not an expert in the greeting protocol either.