By considering values and timings of on-chain movements, they tie pre-mix bitcoins to post-mix bitcoin and conclude that the same operator controls certain deposits and withdrawals from Wasabi.
What does "
By considering values and timings of on-chain movements" mean? Imagine you're monitoring Wasabi coinjoin liquidity and notice that a substantial amount of money enters the system, significantly increasing available liquidity. For example, let's say 600 BTC flows in. You then observe that total system liquidity stabilizes at this higher level—indicating the entity that deposited is still actively coinjoining. At this point, you can no longer track the funds, but you know the entity remains in the mixing process.
Then, you notice liquidity drops sharply—say, by 300 BTC. You decide to trace the outgoing funds and discover either a large consolidation of tens or hundreds of bitcoins, or multiple deposits flowing to the same exchange. Shortly after, liquidity drops again. Following the exiting funds once more, you find additional consolidations or more deposits to that same exchange.
Here's the critical question: what are the odds that 600 BTC entered the system and 600 BTC exited—only to end up at the exact same exchange?

This is why a whale can never hide among small fishes. This is why big consolidating lots of coins is a bad idea, especially for whales and this is why using Wasabi as a mixer is a bad idea.