If we ignore their specific language, the plan of coming up with ~20 pieces of moderate evidence is a perfectly reasonable strategy for correctly establishing guilt, assuming that there is absolutely no mitigating evidence. Your complaint seems to be that they use different language/notation than you and I do to talk about evidence, which seems hardly fair.

I think the assertion is that they appear to be coming up with ~20 pieces of evidence and then trying to say that each piece is very strong - or at least, they have done so for the burglary hypothesis, so they might be doing so for the other pieces of evidence too. Naturally, their methods of making each piece look very strong are flawed.

You almost pinpointed the reason why this happening here:

trying to find many pieces of weak evidence is probably not a good strategy if the goal is to get humans to correctly decide the accuracy of an assertion.

Humans are bad at intuitively handling evidence in general. There is a possibility that this case suffers from a serious malady: presiding judge Massei has decided the correct, accurate decision in this matter is that Knox and Sollecito are guilty, and has strategically prepared the judge's report to get people to decide this way. This hypothesis explains why the judge has produced such a weighty document when 20 pages of it would have sufficed.