One case study was conducted using a Magneto system. This case study shows: we need to carefully investigate the system besides our usual content, design and SEO. Sometimes System itself can results very bad effects on SEO like this case study.
In our example, products are published in more than 1 way (depending on which path you follow — site search, or using menu or searching at Google, etc):
First way: With category listing at breadcrumb
Second way: Without category listing at breadcrumb
When we checked the code, we definitely identified: difference in code (due to breadcrumb urls to categories and subcategories) as follows:
Definitely Crawler will be confused to pick or index – undecided on which one is the right one for indexing ??
In older days, it was called a variant of CLOAKING — giving different contents for a same URL – as the SPAM sites do!
I believe, due to our achieved TRUST (from google for this website [>10 yrs] ), search engine is not penalizing the site greatly. HOWEVER THEY NEED TO FIX THIS PROBLEM. ONE RECOMMENDATION IS TO KEEP THE CATEGORY / SUBCATEGORY INFORMATION ALWAYS WITH THE PRODUCT in order to understand the category information of the product by Search engine.
By the way: When we checked Google’s cached version, we found it had recorded the without-category version – which we don’t prefer (due to the mentioned recommendation above)!