I've just had a quick read of some of the BTEC L3 stuff, and from what I can gather, that is basically what was the old ONC (ONC = Ordinary National Certificate). I seem to recall my certificate just said "National Certificate". So, it would appear that the level 3 thing is what you would need to do before a HNC. Certainly looking at the prospectus of my old college, they describe the HNC course as being level 4 (
https://www.chesterfield.ac.uk/sites/default/files/documents/cc_part-time_guide_web.pdf)
It certainly wasn't wishy washy. I agree that at first read, it looks a bit pants, but things like "electrical principles" and applications covers a hell of a lot. For example, we spent a good chunk of time learning to design a dc motor, right down to the number of turns required on the windings, how many poles, supply voltage, current, torque etc. Then again with transformers, and we're not talking design of a little 5VA thing for a PCB, this was calculating stuff for substation size, taking into account power factors of loads, iron and copper losses (resistances in the copper and eddy currents in the core, not pikeys nicking the metal
). Also designing single and multiple transistor amplifiers from scratch with just the desired impedances and gain specified.
If that is indeed the replacement for the ONC, and you can do it in 12 months as a distance learning course, its well worth doing.