Incorrect on 'linearly'. Bitcoin can theoretically be pruned.
Yeah, I was just being snarky:-P
Monero can't theoretically be (prove me wrong).
And I agree that BoolBerry's pruning probably has a flaw that leads to some divergent scenario such as gridlock. I would need to look closer to be sure, and I don't have time. But I remember thinking about the possibilities in some detail months ago when I learned of Cryptonote and I always thought of divergent scenarios to every pruning strategy.
I don't think pruning is possible, at least not in the way you could with Bitcoin. There are other things we're looking at, but in my opinion pruning is a non-starter for solving this.