I don't think he was necessarily being untruthful - it is just a reflection of varying standards.
For instance in the US, someone can be charged, arrested and imprisoned, awaiting a preliminary hearing, based only on the probable cause standard. The prelim would consider if there was a case to answer, even if the prospects of conviction were far from clear.
HCW was likely saying he had enough to charge, but prospects of success were too low to issue a charging decision (and a court may not support it). You see this also in the UK where law enforcement wants to charge someone, but CPS declines because the prospects at trial are too flimsy.
Many cases are borderline and prosecutors have a lot of discretion in this area.
My interpretation of what HCW has said is that they planned to build the case during the subsequent two years of the preliminary phase, but failed to find the further evidence they needed.
