I’ve observed the effect to be bigger than that. I specifically measured this in June when I got a new drive. I’ve set up a new node and counted the number of ingress requests on both nodes every hour, while switching the unvetted node offline periodically. When both nodes were operating at the same time, the unvetted node had around a quarter of upload requests of the vetted node, and this ratio was quite stable over a week. When the unvetted node was disabled, I had small, but visible increase in the number of requests of the vetted nodes; hard to put firm numbers here, but the 95% confidence interval for the increase was around 0.5%-5% comparing 15-minute intervals next to each other. Not something one would recognize from a graph, but the effect is clearly there.
I was both surprised and satisfied observing these numbers. Surprised, because I didn’t expect the effect to be that visible. Satisfied, as the calculator I made almost two years ago was predicting this effect correctly ^^