Long story short, WordPress has a monumental issue forbidding you to use the same category slug more than once. It disallows you from having a category tree like this:
The system doesn't allow that same category to exist amongst both product types, so you are forced with this inconceivably bad structure instead:
...where the "-2" is forced to be appended to the second set of categories, even though they have nothing to do with the previous ones as seen in "/cars/". What this does is make WordPress a mute point when creating either a multi-country site (mysite.com/us/ and mysite.com/canada/, where both have duplicate site-wide category structures that are canonized) and classifieds or ecommerce sites, where the webmaster is forced to put a "-2" or reword/add unnecessary words to a category slug just to appease the restriction that WordPress' core puts forth.
I've been using WordPress for about 7 years, and this has not only never been fixed, but it never seems to be officially addressed or recognized. It's just very discouraging, especially when you're working on a huge project using WordPress, and suddenly get roadblocked because the software doesn't allow you to perform the most fundamental action of having two identically named subcategories.
Having a storefront that looks like this simply doesn't cut it:
nor does mysite.com/used-cars/used-honda/used-accord/product-listing-here, or any other reiteration or work-around involving the re-structuring of those URLs.
...and I think anyone would agree with that.
Really hoping this gets addressed as it is a major ongoing problem and there are numerous complaints about this on the forum over the past several years. Only a core update will fix this, so, only the dev team has the power to do anything about it.
Thanks for your attention and for understanding my frustration.