There is no need for that. They got the pw by using normal investigative procedures (duh, ask next of kin). Theres no need to lower security just because the FBI or anyone else is to lazy to ask your mom what your pw might be. I can tell you that from first hand experience with FBI cracking procedures, that they can take literally a PILE of documents associated with any case, run it through something similar to John the Ripper and do simple bruteforce attacks but they are more specific to the person. It will go through names, bdays, addresses, etc trying combinations (forwards, backwars, common character replacements, etc) of anything and everything they have ever gathered that is associated with that person. More likely than not, a person's pw is something that they associate with (easy to remember for that person). IMO, this is one of the possible ways that they "hacked" the iphone in CA. The other is simply asking someone what the pw might be.
Bottom line, the FBI was simply trying to use this case as an excuse to be lazy. There has never, and never will be a valid reason that will ever justify lowering encryption security.