It's not so ironic, you can do both. What differentiates what Toyota is doing today from what Toyota did before TPS is, without understanding where the bottlenecks were in their manufacturing operations, the stockpile sizes were uncontrolled and thus only represented waste. Here, lean manufacturing principles still apply, albeit with an intent to pay a certain amount of cost to maintain a stockpile of a certain size, for BCP purposes.
Yes. No buffer is bad, and too much buffering is also bad. It's about understanding all the parameters that determine the optimal buffer size given the goals, and maintaining that optimal size.
