Considering how many Dell or HP machines are used in the enterprise, I would think a lot are opened up at some point.
I would think that anyone with an EPEAT certification requirement would be opening up the laptops at some point.
Most likely they would be corporate, charity, government. It is common practice to have imaged drives and simply swap them out when repurposing or when something goes wrong or even when there is a software update of some kind. This is often a very time effective method and common practice. It is also not unusual to perform RAM swaps/upgrades. Not to mention battery swaps.
I think you are considering the typical requirements and usage of a consumer vs. the requirements of a body that actually cares about EPEAT certification.
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I don't think I've ever heard of a screw coming loose in a laptop. Assuming it wasn't loose to begin with, which I have also never heard of. But I have heard of screws coming loose in people...