Assuming that panel five is roughly the upper inset panel (Boris was there, I'd forgotten that), that was before Agatha was made a Lucrezia host by the summoning engine (and before Klaus was infected by the spark-wasp by Lucrezia-in-Agatha). So while Boris's observation is accurate, it doesn't rule out later corruption of Agatha and/or later infection of Gil or Klaus. Though pre-summoning Agatha could affect wasps and people who were wasped, including yelling at the wasps on Castle Wulfenbach, and causing the audience to kneel at the command performance in Sturmhalten...

Also Dupree knows about & was dosed with Tarvek's anti-wasp potion, and ... probably knows whether Gil was as well, though that didn't appear on the page. Whether she thinks it worked ... no idea.

OTOH, Boris and Dupree have (in theory) had time to catch up while outside Mechanicsburg, and Dupree has had a LOT of time to observe Gil (and Agatha and Tarvek and ...). They may not like each other (or each other's attitudes) but they've worked together for a long time and have some respect for each other's skills. I hope that information's a lot more recent and includes the brainwashing situation(s).