I'd say it was a publicity stunt from very effective brand marketers; they might as well have treated "No Logo" as an instruction manual. The Brewdog logo on the bottle matters more than the recipes to its target market, and the counterculture stance is all part of that. Brewdog's advantage over other craft brewers is branding rather than brewing.
And yes, it's also good for publicity when trying to crowdfund from "the misfits, the independents, the libertines”, perhaps because "the financial institutions of the City [which] gave rise to the bastardisation and commoditisation of beer" weren't too keen on their 115x revenue valuation. Nice of the Guardian to take those claims at face value (linked article) too.
But seriously, I'm struggling to think of anyone in the beer industry that tries to "make money out of keeping beer recipes secret", especially with most of the best-selling beers relying rather less on taste than Brewdog. Coca-cola, of course, famously emphasises their closely guarded recipe, but as with Brewdog's "open source", that's more about the corporate mythology behind the brand than any serious fear that someone might even slightly dent their brand and distribution network by making something that tastes the same rather than merely similar.