The US, along with most countries, has limited the import of certain products for over 100 years. So, this is not only not new, but it is old.
Simply put, the CBP Officer was correct. Others have posted the links to what may properly be imported, but the key is that the Declaration (whether written or electronic) asks about "food" without limitation. Thus, if you have any "food" you must answer "yes". The next inquiry is whether specific food may be imported.
For what it is worth, importing food without declaring it, even if it is OK to import, will almost certainly result in the revocation of GE. It can also result in the imposition of up to a $11,000 fine (not generally that high).