Hi there! There seems to be a bit of confusion in this thread between URL structure and Information Architecture. Having more folders in a URL doesn't reduce the authority but pages with more folders in the URL tend to be deeper in the sites linking architecture, which means they tend to have less authority because they aren't as close to the surface. The difference between internal links and url format is an important one. There's a blog post here which explains in more depth.
From my perspective, here are the benefits of having pages within folders;
- There is an opportunity to put more relevant keywords in the URL without stuffing
- Easier folder-level reporting in Google Analytics, Search Console etc.
- Some increased understanding for Google of how pages hang together - there is some evidence that Google uses folder structure for ranking before it knows much about the page for example.
In terms of managing authority for pages and signals of relevance I'd be looking much more towards the internal linking to those pages. I wouldn't rely on Google intuitively understanding the topical connection between two pages unless both of those pages target that topic or have relevant links between them. So for example, say you have two pages;
- site.com/widgets
- site.com/doodads
If those pages are both subcategories of trinkets you could reformat them to be;
- site.com/trinkets/widgets
- site.com/trinkets/doodads
Having "trinkets" in the url might help both pages rank for "trinkets" type keywords, like "doodad trinkets" for example. However, I wouldn't rely on this change to help Google understand that widgets are related to doodads - you can handle that much more effectively with relevant internal links between /widgets and /doodads that make the relation clear.
In terms of whether there is a risk to making this change - this is essentially a migration and definitely comes with risks associated, even if all of your redirects are 1:1 and direct. It'll take time for Google to find the redirects and new pages, and as a rule of thumb, link equity isn't passed perfectly along a 301 redirect so I wouldn't expect these new pages to just inherit the strength of the old ones.
I think it comes down to weighing up whether the benefits I listed above outweigh the risk of an in-site migration. If you think the keyword targeting opportunities will make enough of a difference then great but I wouldn't rely on url structure as a way to get Google to understand your site differently - the impact of internal links is going to be a far greater factor.