Originally Posted by
mahasamatman
A ticket is governed by its most restrictive component, so even if it is real Y (which it may or may not be), it should have no effect.
I can't think of any scenario under which the fare rules would change. There are plenty of other places where UA uses the RBD instead of the fare class (meaning Y rather than T in this scenario), but I don't think calculating changes would be one of them, since I don't think they actually refare the tickets when they rebook them. For changes (not refunds), the most restrictive language generally only applies to the changed fare components.
That said, OP: if you're too sick to travel, UA will refund your change fees. You may need to get a doctor's note saying that travel is inadvisable.