You could never submit a hard drive as "evidence," because not every little thing on the hard drive could possibly be relevant to the case. And I can't possibly explain why the SO didn't go through the hard drive in more detail.
But I think your real question is, why isn't the hard drive subject to the public records laws? The answer is, it IS--but the SO would have to go through every tiny bit of it (for the first time apparently!) in order to redact anything on there that falls within an exception to the public records laws. For example, there could be social security numbers sprinkled around in there.
Here's the exact answer I got from the SO about the hard drives (I asked for the one from the laptop as well):
I had an opportunity to speak with our computer people regarding your
request. Unfortunately, we cannot fulfill it as worded. Specifically,
you ask for "the Encase copies of the computers"; those copies cannot be
copied and sent to you because the hard drives contain information that
is not public records pursuant to Florida law. The nature of an
"Encase" copy is such that one cannot redact and/or delete information.
As such, information that you are not entitled to would be released in
violation of Florida Statute.
In theory we could make a copy of a non-Encase copy of the hard drives,
however, before releasing that copy we would need to go through every
bit of information on the drive(s) and delete non-public record
information. Conservatively, that process would take a person working 8
hours a day for 3 months to complete. Of course, we cannot devote the
time of our forensic computer examiner in that manner, so the process
will take considerably longer than 3 months. In addition, as provided
by law, before something like that was even begun advanced payment is
required. The law allows us to charge both the salary and the benefits
of the computer analyst who will be required to perform the
review/copying/redacting of the material. A conservative estimate is
that figure will amount to something over $6,000.00.
I didn't want to spend $6,000 and wait 6 months...or a year...or whatever, so I narrowed my request.