why url like this do not work when we try to access to all product of a specific attribute value.
let's take manufacturer as an example:
the manufacturer filter appended like this in the url will only make sense to Magento if:
- manufacturer is an product attribute
- on product page, attribute are not normally used by magento module. So, unless your site has some customisations that read the product attribute manufacturer, then this manufacurer variable will be not used
- now, in category page, this manufacturer may be used but it is still under various conditions