Upon further investigation, I discovered the answer in the IRS Form 8888 Instructions.:
"You may request up to three different savings bond registrations. However, each registration must be a multiple of $50, and the total of lines 4, 5a, and 6a can’t be more than $5,000 (or your refund amount, whichever is smaller)."
Our problem is that the total on our JOINT return was $5000 for myself and $5000 for my spouse, which when totaled ($10,000), exceeds their $5000 limit in totality.
So if you filed jointly and asked for $5k each, they won't do it. They limit it to $5K per return filed.
