Rebol was kind of a grab-bag of agendas, IMO, and I think people were able to "see what they wanted to see" in that. This consensus became difficult when an artifact like Rebol2 was seen as a start... but a start, to what? The ensuing fragmentation is not that suprising.
Tons of languages try to minimize CPU use or memory. Where I saw Rebol as being different was dialecting...to let you pare back the source (or more generally, "right-size" it) by bending words to mean something appropriate to your task.
So looking at the kind of thing you'd probably not do, here's a TLS transition dialect in Ren-C:
Prettier TLS State Tables (and Assessing the Cost)
Small things like that do make the TLS extension load more slowly (substantially so with the parsing being usermode). Multiply that by a lot--because I'm willing to do similar experiments all over the codebase.
But at this stage of the game I feel such explorations are valuable. They're educational, much like people being able to build something like DESTRUCTURE in minutes:
As I like to say, I don't throw softballs. And because I'm liberal in my use and test of such things--including during the boot process--I don't find your comparison table surprising or worrying in and of itself (though it needs to be done right if it's to be done). I'm just not seeking to optimize that statistic for a default test distribution at this time. And I even keep around things I never would have written myself (like the Atronix "locale" extension) because it now and again exercises a case that gives me food for thought.
There's nothing particularly endemic to Ren-C's design prohibiting it from having a build configuration within striking distance of Boron's or R3-Alpha's if it wanted to. There's simply no reason to pursue that. Certainly not to try and get you (or Kaj, or Oldes) to use it...I like to focus on puzzles that might have a solution. 
I'm more about letting people express themselves elegantly in small character counts--and have that expression pull of miracles. In terms of the artifact that does it, I do accounting in the large in terms of dependencies.
But maybe when the time comes, pressures would be such that things like stylizing the TLS transitions is wasteful in the scheme of things. I don't know. It still feels pretty far away to be concerned, especially since the web build doesn't use the TLS extension at all.