Few thoughts on the subject:
1) Since the documents are public, they WILL be vague on PURPOSE - look, its not just bored pensioners or law students who reads them. People who are on the other end in these cases also reads them. Criminals, shady lawyers etc. also extensively look through such documents to see what kind of methods police and prosecution are using. Imho its in prosecution's best interest if the wording remains in a way so that you don't really know if the password was written down somewhere (if all those phones were connected, there literally could be some guy who was ordered to get the phones for his buddies and the criminals simply fucked up because they can't remember a password), whether the suspect told the password, maybe the passcode was literally 1234 or was it some elaborate sting operation or a Hollywood movie style remote access. Similar to any other kind of evidence - police will not publicly disclose how many hours and in what way and with what tools they gathered evidence against somebody, it will probably just say "extensive surveillance" or something like that.
2) for me the weird part was that in some cases they were recording and taking pictures of the screen. If they actually had this sophisticated high-tech tool developed that could remotely attack devices just by knowing IMEI (what was originally posted), why would they need manual extractions and video recording phone screen from another device? Doesn't make sense to me. If they had access to such a powerful tool, you would be seeing noticeable and recording breaking numbers of arrests and prosecutions. Is that happening in Sweden? I think the usual news about Sweden is that the crime and gang problems aren't getting any better...
Imho the answer here is that people should be gravitating to Occam's razor - the police gained access to the phones in one of the many old ways, they just aren't saying it in the documents, to keep it purposely vague so criminals are kept unsure on how police work.