Aha! I’m glad you asked this, because this is at the heart of why this method works so well… No it’s definitely not the same… and here is why…
Take a snare drum - you can clip a snare drum much deeper than you can, say a vocal, or say some cymbals, or some other other musical instrument like a piano. By clipping or limiting the individual sources, you are tailoring the type and the amount of clipping and or limiting to suit. You have control over it individually.
When you slam all your stuff into a limiter on the 2 buss, it gets limited all the same amount. Some of that will be favourable to some the of programme material, while at the same time being devastating to other sources fed into it. The only option in that case is to reduce the amount of limiting until the devastation is minimised. Taking care of it most impactful sources “upstream” minimises the what you have to do at the end, and the net result is that it can sound better.
It’s the same principle as to why we use multiple stages of compression. Each earlier stage lessens the work needed by the processors in the next stage. So if you goal is to not “hear” compression working, then condition the material going into the compressor.
There is also the fact that transients in heavily rhythmic music compound, because they tend to all happen at once. If you tame each individual transient at the source the compounding effect of them is lessened.
committing the same crime
A “crime” is good analogy that actually illustrates the point:
Who is likely to be the more successful, wealthy and uncaptured criminal? The guy who walks in the front door of the bank with a balaclava and a sawn-off shotgun demanding money; or the quiet, nerdy computer geek who comes up with a way to silently skim a few dollars each from millions of different bank accounts?
Little gains add up to a lot, and can be pretty much penalty-free.
…I dunno, Adrian, I could talk all day trying to prove to you why it works. Ultimately, that is meaningless. If you care, try it; If you don’t, ignore it and carry on as you were.