This rule applies only to those Signature Campaigns where payment is made in bitcoins. If the OP decides to apply for Signature Campaigns with payment in altcoins, then he will probably be accepted by the manager, since the number of applicants in such campaigns is unlimited.
Yes you are right that mate Op can apply a campaign that pays Altcoin which is we are all know that there no other requirements on that campaigns as long as you have social media account then you will qualified. Cause some of them are offering redit or in tweeter which is we are all know that This is one of the most active social in every country around the world .