People keep misreading this, or maybe just looking at the headline and getting the wrong impression.
The news in that piece is that NY discovered the transfers at all. The transfers themselves are a decade old. The payments to the Sacklers from Purdue are from 2008-2016 but the lawsuits only date to 2018. All of this is in the article if you read it.
I.e., no self-payments after lawsuits became material threat.
"Sackler was involved in 137 wire transfers totaling nearly $20 million, and some of those transfers occurred as recently as 2018, the filing indicates."
Those substantial transfers ($1B) were a decade ago.
The sentence you quote does not appear in the NYTimes piece and is, in comparison, peanuts. I do not have access to the Bloomberg piece for full context, but the sentence you quote does not say the movements were self-payments from Purdue rather than just personal transfers between personal accounts. It also does not say all $20M was in 2018; there could be a $1k wire in 2018 for all we know from the single sentence.