We have a website with multiple product verticals which are independent sections (first section has sub-directory example.com/section1, second one has example.com/section2 and so on for other sections).
Would we face any issues if we were to add breadcrumbs to a particular section but not add them to the other sections from an SEO perspective? Would we get the benefit of Google being able to understand our page content and hierarchy better for the pages which do get breadcrumbs?
Google follow markup on page itself, it does not care about your directory/section. If some pages have markup and if it follow their markup guidelines, then it will display rich snippet into search results. Schema Markup is page level not section/directory level.
And Schema does not influence in ranking/SEO directly, but may help you to get better CTR because it may display nice snippet into search results. But from an SEO perspective it does not matter, there are so many webpages on IMDB website, on which few pages have markup and others doesn't have any.
