Yes. In fact, marketing will always never fail to promote any tool-free slot covers in their casing and even if there is no marketing, if you look closely at pictures of the casing, as long as you see a long line of screws on the slot covers, the slot covers are replaceable. Break free slot covers are always a hallmark of budget casings and are frowned by case reviewers as a sign of cost cutting.
They dont really save a lot since its always mass produced and their cost per unit is insanely cheap, but yes still savings nonetheless when spanned out across tens of thousands units.
However its also because those budget cases usually will never see the light of a new GPU/PCI slot component hence its a useless feature if they included replaceable slots in those cases. All systems that I've bought cheap cases with punched out PCI slots for, the users will never ever change the GPU or remove anything until it finally dies or gets too old and slow, which by then its probably time to overhaul entire unit.
I think casings' web page and specifications usually also never indicate explicitly whether the slot covers/brackets are detachable and replaceable or not. Only state the number of slots available.
I thought the tool-free usually is for the HDD/ODD installation?
Its usually pretty obvious. General guideline is most cases above $100 usually comes with replaceable PCI slot covers. Also you can easily find out by googling. 100% can find the case you're looking for unless its some no-brand no-name case.
Tool-free simply means no tools(screwdriver) required, it doesnt only apply to HDD/ODD, it can apply to anything that is "tool-free", meaning they have some kind of holding mechanism in place so you dont have to manually screw stuff in. Its just a very stupid marketing phrase really. The only tool-free PCI slot I know of is from Lian-Li