3-pin floating preregulator

Hello. I was investigating on the possibility of using of a tracking preregulator, also for fixed load:

Using 3-pin regulators off-piste: part 4

if I well understood, this has benefits on line regulation (and noise) by separating line and load regulation for optimal perfomance. What's not much clear to me is at the end of page, when he says about the LM7805, how it comes to be linked to the 2nd regulator...more, the common pin of the LM7805 couldn't generate stability issues by connecting it "bare" to Vo?
 
Yes, the last part is speculation. I don't know if anyone has bothered investigating whether a 3 terminal regulator would be more effective in simple series with the final regulator, or instead specifically a 7805 tracking the output of the final regulator.
 
How so?
I've always had 100 percent success with that design.
The resulting DC is as pure and noise-free as using a battery.

Sorry, I misunderstood, sometimes I mess with english. I said about the tracking preregulator: I meant that the author doesn't go deeply into discussion to make the reader out, I think..,your approach is simple and right with the capacitance multiplier.