It is absolutely correct to say that the GSEs allow for use of EAs.
It is even more correct to say that they allow EAs only when requiring some sort of inspection and using CB4 in the reconciliation section.
One cannot, for example, just insert an EA in a text addendum, because doing so is contrary to the SOW statement that says that one cannot add assumptions (an EA is an assumption). This is an intentional construct - as risk cannot really be managed if one allows for the addition of unlimited assumptions.