Recently I was playing my custom map "The Inside Job" for the first time.
It employs small pools and ridges (if you play you'll understand what I mean).
It doesn't have much space to build on the protected level 3 (base level is 2) so while planning as the game ran I realized that a pool is an easily defensible position (or at least below a cliff).
The creeper flows downward at a slower rate then it spreads around, probably due to surface tension and the fact that it has a very high viscosity. Blasters can easily hold their position under the ridge.
Evaporation occurs at the edges of creeper. This has an effect in slowing the outward spread of creeper's leading edge, so that the leading edge advances more slowly than it otherwise would. I don't think surface tension is really modeled - creeper is basically a cellular automata simulation.
The original CW1 flow algorithm is modeled after heat simulation. Kind of funny if one thinks that it's blue and many players associate it with water....
Anyway, that's why it may spread up a level after a while, and while it's slow to propagate
That's where I heard that, then - I wasn't aware that the nature of the sim changed, so I had just thought I mis-heard it.
I know this post is off-topic, but thanks for pointing that out, G.