I did not find the upgrade available from the regular account website. But when I went to the linked fiosquantum50 site, they did indeed offer the $10 upgrade.
But when I clicked on the upgrade I get:
We Apologize For The Inconvenience
Thank you for your interest in FiOS Quantum.
The speed upgrade is not available to you at this time. See other product options.
So it really isn't available to everyone.