I suspect that Apple is afraid that if the reasoning behind this became public that Apple's stock price would be strongly influenced and so they are trying to hide the information from the market. It will be interesting to see if there will be a net negative from the effect of the hiding by itself, after all now people are free to speculate and they might go further in their speculation than the actual ruling.

Apple has filed a court case to block the publication of a report. Obviously the contents of the report will be discussed as part of the hearings. So if the hearings were public then the contents would become public as well, which would make the court case pointless. Hence the private hearings.

Not entirely illogical, if something is expected to generate a lot of media attention, the case may be kept private to prevent the 'court of public opinion' to influence the outcome. Everything is still documented and shared afterwards regardless of the outcome.

Most court proceedings in The Netherlands are not open to the public or press, mostly for the privacy and protection of those involved with the case.

Unlike the US where court cases are publicized and disseminated widely with the charges, but never with the outcome of the court case.