I'm not thrilled with it, but it may just be a reality. They may be using an algorithm that adjust the number needed on the fly on items where scarcity of materials isn't a factor. Example, if they have a campaign for 2 weeks and 200 units and they get orders for 150 units in the first 9 days the algorithm may do nothing, but if they get 150 orders in the first 2 days, it may up the number of units.
I think it would be better if they took the approach of: We need 200 units to make this worthwhile, but if we get the 200 units before the 2 weeks we'll keep it at 100% an inform everyone 2 day last chance to get in if your not in already and then it closes. Its a better optic for the customer to know sooner that a campaign will definitely happen, than to see that percentage not move while the time ticks away. The lead time from a campaign closing to shipping is like 2-3 months, it shouldn't be much of a problem for the factories to make the few extra units, (which they are making with the current system anyway).