The perceived Left policy in the UK has little to do with unions as such. Here is how the International Business Times describes the SNP aspirations. Whether justified or not, something like that is the perception of the SNP among left wing voters, and it seemed attractive to that sector of the population.
I truly think that a) you're grossly overestimating the political nous and analytical ability of the majority of the electorate, b) you're underestimating the emotive power of nationalism, and c) you're underestimating the way in which irresponsible political parties can miraculously promise "jam tomorrow" to voters as a means to gain votes.
On (a), I doubt that if you asked a sample of 100 Scottish voters to differentiate the policies of the SNP and Labour on (Westminster-based) issues such as education, health and management of the economy, any more than 25 of them would be able to answer correctly (or even near-correctly). I suspect that a fair minority of Scottish voters don't even know what the difference in powers and responsibilities for Scotland is between Scottish MPs in Westminster (and the Westminster government/parliament) and MSPs in the Scottish Parliament and its government.
On (c), I found the following passage from that IBT article you quoted to be interesting and relevant:
If the SNP gets its way on every front, austerity will end, the creeping privatisation of the National Health Service south of the border will be reversed, the minimum wage will be sharply increased, nuclear weapons will be relinquished, and Britain will join countries like Ireland in recognising that military adventures abroad can only take place with the explicit authorisation of the United Nations.
With the exception of the last clause, the other bits are either a) not without serious implications or risks, or b) total cloud-cuckoo land stuff. I love how parties can say, with a straight face, things like "Under us, austerity will end!". It gives a significant proportion of voters the impression that abandoning austerity
policies (not austerity
per se, note....) is a cost-free alternative with no downside, where everyone can suddenly live in clover once again. Likewise the funding and organisation of the NHS, the policy on the minimum wage, and (to a lesser extent, admittedly) the policy on nuclear weapons.
Having seen some of the economics stuff the SNP has put out, and having seen what it's done (and not done) so far in its Holyrood administration, I strongly believe that the SNP will disastrously fail in its quasi-utopian approach to economic stewardship. Most of its economic policies are the sort that may appear superficially attractive on paper - especially to unreconstructed socialists - but in practice they're doomed to disastrous (and very costly) failure. One only need look at the socialist mess that the Welsh Assembly made of the Welsh NHS as a primer for all this: Welsh voters were seduced by the idea that all prescriptions would be free, and that social healthcare and outpatient services would be hugely ramped up. Sounds fantastic, doesn't it! Only problem was that in practice, Wales couldn't afford these levels of support and service, and as a result NHS Wales would be in administrative receivership by now if it were a commercial business.
I sincerely hope that the SNP - both within Westminster and the Scottish Parliament/Government - soon apply a good dose of
realpolitik and pragmatism, and realise that idealism and practical reality are two very different things. Somehow I doubt it though. And that's why I also think there's a good deal of truth in the somewhat Machiavellian rumour that Cameron is being urged by his own party and Labour to give the SNP even more than it was asking for in Devo-max, as quickly as possible, on the premise of the old adage of giving someone enough rope to hang themselves.....