The 6.0 release for Java Static Analysis has resolved a lot of FP's that existed in previous releases and both our source and byte code Analyzes (byte code Analysis used for function summaries) are now much more precise. It is therefore very possible that a mistake made by our 5.5.3 Analysis, which you corrected with a custom model, is no longer necessary in 6.0.
But keep in mind that modeling is much more important in C/C++ than in Java where resource allocation/deallocation, asserts and exits are all part of the Java language and understood by our Analysis out-of-the box.
Note that if your FP's re-appear in 6.0, please file a case with support. Modeling is not always enough, checkers may have to change too, so an actual example of a problem that may be resolved with modeling will be helpful to us as we re-introduce custom modeling in our fall release.