Ravnos Carnival: is cost announcement binding?

[RTR 20111202] indicates that the number of tokens used on the Carnival should be announced. Is it binding? (as in, do you fizzle if you loose blood even if you have enough counters? Can you change your mind if you gain blood and use less counters?).

I ask because this is listed as a mere fix in an outline, but if it is binding it would contradict the earlier [LSJ 20090201] . And if it's not binding, one could wonder why bother with the announcement.

Maybe consider what this entails for other effects such as Nergal's reduction ability (see [LSJ 20091021] ). If the announcement is indeed binding, is this also a reversal on some of the answers on Neural ability's use? If yes, which?

I would need an RD answer for reference.