It really sucks that checkout attributes just apply to all products, not very useful, at least in our case.
Wouldn't product attributes be better suited if you want the attribute for specific products? But if your requirement needs to have the attribute at the cart page instead of the product detail page, and make it only available for some particular products then yes it is not available out of the box and may need some customization
Yes, as per the documentation, the conditions are only based on a previous checkout attribute:
...can specify a condition for the checkout attribute to be visible (depending on other attributes). A conditional attribute only appears if the previous attribute is selected.