Two ways to look at this chart...One way is to say that Dak is #4 in the league. The other way to look at it is that the difference between #1 and #4 on this list is pretty similar to #4 and the next 20 or so QBs.
I'd like to see the actual data on this chart to understand the whole picture. For example the difference between Dak and Daniel Jones seems to be roughly a 5% conversion rate or so. Dak has 101 3rd down attempts this season. 56-101 w/ 917 yards 8tds 7ints to be exact. Daniel Jones was 75-130 w/ 783 yards 3 tds 1 int.
Do with those numbers whatever you want, there are good and bad talking points for both players there, but making a chart on 3rd down conversion here is dangerous given a small sample size (roughly 100-150 attempts per qb) and less than 10% differential separating most QBs on the list means that we are really talking about just a handful of plays that separate most QBs on the list. What I'm seeing here is we have two elite QBs in the league (Mahomes/Allen), 1 second-tier player (Burrow), 3 awful QBs (Wilson, Mills, Mayfield) and everyone else all roughly within one standard deviation.