Background
One comment on this question about Robert Mueller's 2017 Special Counsel Investigation inquired about a specific aspect of the investigation. This aspect related to the prosecutorial decision making of the Special Counsel:
First, a traditional prosecution or declination decision entails a binary determination to initiate or decline a prosecution, but we determined not to make a traditional prosecutorial judgment.
This specific portion seemed to cause a surprised reaction, as well as confusion given the apparently opposing views on the indictability of a president by federal authorities. Knowing the uncertainty about this aspect of federal law, both @Keith McClary, the person who wrote the original comment prompting this question and I wondered...
Question
In the 2017-2019 Special Counsel investigation, why wasn't the initial decision to make a non-traditional prosecutorial judgment made clear at the beginning of the process?