Did we just jump 500 years into the future, or progress through time naturally, where people update records according to changes in society and technology?

I get what you're saying, but we still have records older than Pompeii itself, and recording methods weren't even a fraction as good as they are today. If covering the site back up adds another layer of preservation, then by all means. But we can't recreate the conditions that preserved it so well to begin with. I think the experts know what they're doing.

One reason that I personally think might be a good reason to cover it back up is because it's essentially a mass grave. People were frozen in time, doing whatever they were doing when the eruption occurred. It might be respectful to the dead to leave them there.