To add to what others said on it: no, you don't. You would if the manufacturers provided full specs, data sheets and CAD drawings of the internals. They don't, for obvious reasons. What's worse, the whole point of a sales copy is to confuse you about what you're getting - providing disinformation, in form of vague promises of emotional effects and feature statements so broad you could drive an aircraft carrier through. A lot of consumer laws exist to counter this dynamic.

> Open Source wouldn't exist without that

It would, if the software was also free :). This is a longer topic, but there's an argument to be made that software industry is in its sorry state precisely because it's allowed to sell software "with no warranty whatsoever".