Hi thedeadseawasonlysick,
Not doubting you at all... and what the Jepp tech told you about solid state was correct - a solid state unit would never have a problem with operating at high altitude.
Having said that, the the statement about standard hard disks failing sounds very much like a myth, possibly interpreted from disk drive tech specs or, worse... the Internet.
I work for a disk drive manufacturer. These days, hard disks end up everywhere. We just don't see this kind of failure.
Specialist drives are available which are tested to higher altitude operating conditions than regular drives. In most cases, the only difference is the testing process, not the manufacturing line.
If you were operating an unpressurized aircraft at high altitude, you would be well advised to go for a specialist solution to ensure that the equipment would operate for prolonged periods.
You can always build in redundancy (for example, two laptops, each with different manufacturer/model drives) if you are solely relying on electronic charts.