Anyone know whether GUCs can be applied to a reservation with a lap infant ticket?

I see under the GUC T&C at https://www.delta.com/us/en/skymiles...lion-upgrades: "4. Not Combinable:  Valid only with a published qualifying fare, including corporate fares and tickets booked as part of a Delta Vacations package, with a ticket designator beginning with the letter `X`, ‘Y’, `C` or `A`. The certificate is not combinable with any other ticket designator programs or special status fares such as: Government, military, no-value, VUSA, round-the-world, agency/industry discount, group, senior, student, infant, child, coupon, certificate or any other fares/tickets which may later be specified by DL with or without notice."

Does this mean GUCs can't be used at all?