I wouldn't know where I was supposed to draw that dotted line if it weren't already there. And I'd expect there to be less variance in vote percentages among machines that processed many votes than those that only processed a couple. But okay, that picture shows that Trump overperformed in the early vote among machines in Clark County that processed many votes (and that Harris overperformed among those that processed few.) Couldn't this effect emerge from the geographic distribution of voting locations? The points at the right of the scatterplot would tend to represent red rural precincts serving many early voters, while those on the left would represent urban areas denser with machines than they are with early voters. (And there are other considerations, such as that Trump voters may have been more likely to show up in person to early vote than to mail in votes. The vote totals by voting method would seem to show this—but, fine, they're under dispute here.)
These analysts acknowledge the "deep red areas" explanation in their pdf, but they handwave it away in an unconvincing way: they say that the same effect doesn't occur for election day voting, only the early vote. But most voting in Nevada doesn't happen on Election Day. According to the data they present, every single voting machine in Clark County processed less than 150 election-day votes, with most well under 100. That is, they'd all be well to the left of the dotted line. So even in the vote-manipulation scenario, these analysts should expect to be seeing no separation effect for the election-day vote. Its absence tells us nothing.