wizard values were saved in the storage variable of the form_state object...

wizard values were saved in the storage variable of the form_state object which would ultimately create problems during form caching if something like a node entity or user were present as part of the wizard cache_values. This is unlikely, but in the case where a wizard generates multiple entities at the same time, it seems likely that the full entities in the wizard values would be favorable to just arrays of values, so the wizard values have been moved into form_state temporary storage which is removed before forms are cached