The threshold for the petition only requires about 6 percent of the electorate to actually sign the petition, so you'd only need about a third of the people strongly in favour of separatism. That's why the threshold for the referendum was lowered this much. In my opinion, it basically makes the petition passing inevitable. It certainly could be that the 30 percent who are slightly/strongly in favour of separatism are actually an overrepresentation in the polls due to various reasons.