In my understanding, doing accounting on accrual basis involves much more than using the business features of GnuCash. It is a discipline to be followed, not a technical aspect of the accounting tool. But if we can seriously discuss the matter, then the first problem is that GnuCash documentation currently warns that users should never manually add accounts to the classes "accounts receivable" and "accounts payable", because these classses are exclusively reserved to the GnuCash business features. Therefore, there may be other accounts that belong to these classes by nature, but are not explicitly classed as such. So either the documentation should allow the user to use these classes outside the business features, or GnuCash needs to provide some other way for users to tag accounts with this property. Only when an agreement is reached for this problem, is the time to consider which reports and other features (such as closing books) are affected and how.
In my understanding, doing accounting on accrual basis involves much more than using the business features of GnuCash. It is a discipline to be followed, not a technical aspect of the accounting tool. But if we can seriously discuss the matter, then the first problem is that GnuCash documentation currently warns that users should never manually add accounts to the classes "accounts receivable" and "accounts payable", because these classses are exclusively reserved to the GnuCash business features. Therefore, there may be other accounts that belong to these classes by nature, but are not explicitly classed as such. So either the documentation should allow the user to use these classes outside the business features, or GnuCash needs to provide some other way for users to tag accounts with this property. Only when an agreement is reached for this problem, is the time to consider which reports and other features (such as closing books) are affected and how.