Yes, you can go to any random store that has a Dell laptop you want or whatever and be reasonably confident that it hasn't been tempted with between the factory

Yes, you can go to any random store that has a Dell laptop you want or whatever and be reasonably confident that it hasn't been tempted with between the factory and your purchase, if that's the specific that you are concerned about. However, if you want a one of Purism's laptops, you can't just go out to any big box store and grab one; there's really just this one purchase of option - shipped by post, and if you are worried about interdiction, it's a pretty risky one you would be reliant to opt for. So Purism is providing an option that mitigates that risk, allowing them to capture a market segment that naturally aligns with their product offering but would likely pass on them without this risk mitigation process.