In one of your posts you says your DC gets to choose a book from their library but it's always too hard so it's expected you read it too them, so that is an opportunity to learn new things, in a book they chose, but just to do it with you at home ?
If you know by a comment of "happily chats with friends" was a more generic comment and couldn't be aimed at your child, maybe they are focussing on that and spending time encouraging and helping them be more confident in talking with peers to set them up for next year.
Of course a school shouldn't leave your child stagnant in their learning, but I would think they are spending that time helping them progress in other areas.
Knowing "lots of other children in other schools" on higher book levels in reception, doesn't help resolve your issue, (and don't let it become a competition, comparisons are really unhelpful as each child is so different).
When have your parents evening been and when was your last one?
Our DS is the baby of the class and flying as he is ahead of their reading, but we provide books at home for him to nurture that as I understand that reception is about so, so much more than academia. You won't get any piece of mind until you get a clear answer from the teacher, have you arranged a meeting or are you trying to have this discussion off cuff at pick up or drop off???.
We have only had one parents evening about 2 weeks after they started so basically, it was a meet the teacher and basically your child isn't an emotional wreck when they are left or isn't running riot in the class, as the teachers had really not had a chance to evaluate anything. We get a couple of little online updates, but providing our child is happy, at this stage, we trust the school know how best to make the school transition the best for our child. At this stage anyway.