You can take something philosophical from it, but I think these discoveries are common largely because they are the only kind of discovery you could make.
"Neolithic peoples behave as expected" is hardly a good headline - and though I don't know much about archeology, it seems like archeologists would be scientific enough to not attribute behaviours and technologies to Neolithic cultures for which there was no evidence.
Considering as well that the past is poorly documented (especially wood), discovering something not already known may be easier than we think.
If archaeologists have only come across tool X in cultures which engage in (say) year-round agriculture, they'll fairly naturally come to a weakly-held belief along the lines of "cultures which invent agriculture tend to also invent tool X soon afterwards".
Then evidence comes along of hunter-gatherers with tool X, and someone trying to make a rather dry press release into something more exciting writes "archaeologists are stunned because they previously believed that hunter-gatherers were foolish primitives who couldn't possibly have invented tool X".
That's a good point about what is a form of survivorship bias in science and journalism, but there are not just cases of "we hadn't seen this technology until later" but also cases of "we had seen a lack of this technology later".
I'll admit my thinking on this is very seat of the pants. I'm sure historians, archeologists, etc. think about this plenty.
"Neolithic peoples behave as expected" is hardly a good headline - and though I don't know much about archeology, it seems like archeologists would be scientific enough to not attribute behaviours and technologies to Neolithic cultures for which there was no evidence.
Considering as well that the past is poorly documented (especially wood), discovering something not already known may be easier than we think.