Search index as custom view for taxonomy term with hierarchy. Showing all children results in term parent in taxonomy menu
If I'm understanding correctly what you're asking, here are some tips.

Under your defined search index, go to Fields. If you have "Products" taxonomy defined, uncheck the taxonomy term, then go to the bottom and open "Add Related Fields" and add "Products", then save changes. When it reloads, you'll now have more taxonomy options. Check "Products >> All parent terms". You should now have additional facets for parent/child terms.

Use in conjunction with Facet API Pretty Paths for even more powerful usage. Take a look at one of my other response about how to use that.