Your thread title says "FCC". FCC stands for Future Cruise Credit, and that has only been given to people who had cruises booked that Disney cancelled due to the pandemic.
What I can see now that you're really referring to is OBB, which stands for Onboard Booking discount. When you're on the cruise, you can do an onboard booking that will take 10% off the base price of a cruise you book onboard (unless you book a blacked-out cruise date or book concierge level). You don't get a voucher for OBB, because it's the booking of an actual cruise. You can change your cruise date & ship later on if you wish, and you'll still get the 10% discount. However, the money from this OBB cruise cannot be "applied" to an existing cruise.
Some people who want to get the 10% OBB discount, yet are waiting for a later cruise to be released to apply it to (for a later season that
DCL hasn't yet released), will book something onboard called a placeholder. This placeholder can later be applied to any cruise that you later book (as long it's non-concierge & not on a blackout date). You cannot apply the placeholder to an existing cruise.
So the answer is still no, unfortunately.