Ok, went through the Bort stalker thread. His actual words are a bit ambiguous, but I think they support my version. This is from p. 16, if anyone cares.
Bort: Yeah they'd be pretty good, but not a huge ton better than 11 really, based on the way that most of them work. Yes it would take a while to get something to lv 15, not to mention all the SP's you have to spend to get to lv 10 naturally!
Nixx: Interesting. Kind of diminishing returns, logarithmic scale or whatever? Going from 9 to 10 gives more than going from 10 to 11?
Bort: Sorta; there's just some special stuff in there for stuff greater than 10 to keep things from getting horribly broken (like autofake every time or something LOL)
Later, which clinches it for me:
TSE: What about the difference between 1s and 5s? Is that change far more significant than 5-10? Does it work such that 0-1 is worth the most, then consistently decreasing in value as you move up?
Bort: No, just points over 10 are specially treated.
I'm right
Right?