For "all intent and purposes" is not the same as what the actual determination is. Though you chose to make this determination, as many others have, it is not technically correct.
The GJ job was only to determine if there was sufficient evidence presented to determine if there was probable cause that a crime was committed. Their job does not extend to determining actual innocence. They are only working with evidence that is available at this time, without the benefit of all evidence that might be gathered in the process of trial. Moreover, they are working only with the evidence as presented by a single party, with the benefit of argument.
Contrary to what you learned on Perry Mason, the actual innocence of a defendant is not relevant in the indictment process, nor is it relevant in trial. A trial either proves guilt or defaults to innocence, it never is designed to prove innocence. In this case, the GJ merely weighed whether sufficient evidence was presented to provide probable cause that a indictment should be made. They found that evidence, as presented, was not sufficient. Whether a crime was committed was unproven, hence by the logic of our legal system with its default (presumption) of innocence, only then can you infer a crime was not committed. That conclusion, however, is just that and does not mean that the crime did not exist; it only means there was not substantial basis to say that it did.
As a matter of illustration, for "all intent and purposes", the jury in the OJ Simpson decided he did not commit the murder of Nicole Brown. They never decided on his actual innocence, but we defaulted to presumed innocence. Now would you like to take the position that the jury heard all the OJ evidence and returned a verdict, therefore he did not do it?
But, Holy *****, I find this particularly curious that you are suddenly touting the verdict of the court as gospel given that you have repeatedly argued that Michael Dunn is innocent, even though a court of law, having considered all of the evidence, found him guilty. Somehow I see some selective logic being applied by you in this.