I love the non-Scottish people coming out of the woodwork trying to be experts on British politics. The SNP threaten to leave all the time, they lost the last vote by a landslide but they basically have to keep the threat alive to keep the money and powers coming from Westminster.
The SNP also mismanages many Scottish councils and there is far amount of sleaze associated with their members but it's "our sleaze" and not theirs so it is better.