In the Google SEO Office Hours June episode, a user asked why Google shows structured data errors but not on schema.org. This is because Google Search Console is showing errors for invalid enum value in field "returnFees" but the user’s schema.org test says no error.
Martin Splitt responded that schema.org is an open and vendor-independent entity that defines the data types and attributes for structured data. Google, however, is a vendor and might have specific requirements for some attributes and types in order to use the structured data in product features, such as their rich results in Google Search.
So while just leaving out some attributes or using some type of values for an attribute is fine with schema.org, vendors such as Google and others might have more specific requirements in order to use the structured data providef to actually enhance features and products.
Another user asked how Google treats structured data with parsing errors and Gary Illyes responded that if some structured data doesn't parse, they can't extract the information that it may contain, so it's just ignored.
Have more questions on Google’s use of structured data? Check out Google’s documentation on it here.