Not sure why it would to be honest, "normal" PCs are modular and upgradeable so anyone selling them isn't going to be able to offer a warranty on the condition the case is never opened because opening the case is something the owner would be expected to want to do.
In England, companies go out of their way to avoid a claim on a warranty!
Yep. When I bought mine from a UK specialist builder they sent it packed with foam inserts for transport, and several integirty stickers. The instructions were to remove the case side, remove the packing foam, replace the case side, test the system then put integrity stickers over the gaps and send them a
photograph of the intact seals to activate the warranty.
Needless to say I told them I would treat any individual component failure as an individual fault and would exercise my rights accordingly. To be fair to them, even though the hardware was fine I did have some configuration issues that they helped with even though I hadn't "activated" my warranty. I got the distinct feeling that the sticker thing was there to protect them from end customers who didn't know what they were doing, rather than enthusiasts who did.
These days in the UK the savings made by building your own system are slim to nil, unlike 20 years ago, but the experience can be useful. Then if you do buy an off-the-shelf or custom system in future you can do your own upgrades and repairs without sending the whole thing away.
Good luck OP. I hope your system is back in the land of the living soon.