You both are sortof correct but not quite.
1. Testimony is evidence. As was Jay Ward's report. As I can recall, Jay Ward's report was not entrered into evidence (I am not 100% certain of this though).
2. Prosecution did not hand over the MFT file to the defense until the trial was underway. This was central to the Jay Ward testimony, because it was the MFT data that Jay Ward analyzed. Part of the prosecution's argument was that Ward was not qualified to extract the data. The prosecution also argued that they provided all the data to the defense because they provided a copy of the original hard drive, from whivh the MFT file was extracted, then hid behind National Security to avoid giving the defense the MFT file extracted by the FBI. This is where Boz got really deceptive, because he repeatedly claimed that the defense had all the data for an extended period of time, which was an outright lie.
3. When Ward was excluded from testifying as a forensic expert due to his inexperience with the extraction tools, theoretically this would have tainted the extraction that he performed in order to generate the MFT. The defense attempted to circumvent this by offering to have Ward testify based on the FBI-generated MFT file, which was nearly identical to the one created by Ward. The court erred when he was restricted from testifying about the FBI MFT file, as his experience in examining computer data for intrusion was far superior to the jury's, and this did not require experience using forensic tools.
4. Massucci was restricted from testifying because he was not on the witness list, and therefore this violated discovery rules. The appeals court found that the trial court erred in restricting his testimony, because the defense was not using Massucci to gainan unfair tactical advantage (he was going to testify to basically the same thing Ward was), because there were alternate options available to the court besides restricting the testimony, and because his testimony was central to the defenses case following the limitations on Ward's testimony.
The net result was that a critical piece of evidence was withheld, and that was the expert opinion that BC's computer had been tampered with and that the files that directly implicated him in the killing were placed there by a third party.