"that's an easy comment to make that very much fits the zeitgeist" .. "'build it and the money will come' strategies fail"
Hold on - the point I'm making was not the cliche "build it and they [customers, users, investors] will come. The point is that in the very specific micro-seed stage of companies, which is what YC/Seedcamp are dealing with, the first thing you need to spend time on is the product/core business idea. If you work on this, you'll have something tangible at the end of the 3 months, that you can then show people to get to the next stage.
If you don't build something (doesn't have to be a launched, fully funcitoning, customer-ready product) then how can you expect to achieve anything more than more seed funding, this time having demonstrated that you may not deliver in time?
"The YC-like approach could be caricatured as 'shotgun'"
Curious metaphor, but yes, this is the point. Find out as soon as possible what's going to work, and avoid wasting time on stuff that doesn't. If what a team does first doesn't work, they've learnt a whole lot about what to do same/differently with the next idea.
"but copycats don't deliver these [value added factors]"
Yup - correct. This is the big problem. But notice that the things that e.g. Seedcamp lacks are things that have been earned by YC over time, mostly down to previous success. You can't solve these problems by organising more theoretical lectures for the teams.
"The key is to make sure both launch-drive and business training/mentorship are provided in equal amounts"
No. This is the whole point. Having received micro-seed-funding, you need to get somewhere, fast.
Seed funding like YC/Seedcamp is about raising enough money to get to a stage where you can raise a proper angel round/series A. Spending 50% of your time "learning business" will definately benefit you as you go though life, but won't give you any deliverables to make your company succeed in the short term.
Either decide you want to learn business, and then study that before starting a company and getting funding, or concentrate on building your product and then learn about business by doing it for real once you have a real-life case study to work with.