Hashrate is the only good metric denoting how fast the blockchain really settles, so it's great to see difficulty as a lagging metric grow.

The only secure way to leverage settlement on Bitcoin is to wait approximately until ledger costliness reaches the value of the transaction.

So, to settle a billion dollars in Bitcoin and rest assured it's final settlement, one needs to wait a bit. The more is spent on mining, the faster this settlement happens

(from: http://www.2minutebitcoin.org/blog/its-the-settlement-assurances-stupid-2019)