[jstanley]

Don't you want it to stay low for ages and then shoot up all at once?

How does oscillation help?

[fragsworth]

You are right, and they probably mean the reverse causation. If it is volatile, you want to "dollar cost average", so you aren't significantly impacted by the price of a single purchase.

[brndnmtthws]

'oscillation' isn't the word I'd use, but I assume the parent is referring to dollar cost averaging: https://www.bogleheads.org/wiki/Dollar_cost_averaging