This is true, but
"people are unable to retrieve roughly 50% of information one hour after encoding" (
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4183265/). Memory distortion can happen all kinds of ways, but it doesn't take very long at all for it to happen. The idea that after
9 years they would finally decide that maybe the witness's memory might be degraded, that ship has already sailed around the world several times.
Prosecutors will wait until the end of time and still trot out memory-based testimony (as long as it still supports their case), so I think the claim about why they dropped the case is specious.