The point wasn't that they were choosing specific transactions, but that they were such a high percentage of the whole network that it resulted in that.
The extent to which that participation was useful in undermining the network was undetermined.
Discussion
Show us the report
I was wrong, or at least, passing on unverified info.
Sorry.
The info I shared was not from an article, but from a twitter account that has since been deleted. The post did include a link to this article:
https://www.wired.com/story/monero-privacy/
That's a different thing altogether.