The biggest factor here is pure volume. Couch and Winston had a career high in attempts under Arians, Luck and Brady (on pace) had their second most attempts in their first year under Arians. Again, Palmer is the odd man out here with just his 4th most pass attempts in his first year with Arians. It's a fun graphic to look at, but I don't see anything to be gained from analyzing how terrible QBs (Winston, Couch, Luck as a rookie) played in their first year with Arians. Palmer is the only useful data point, and it's exactly 1 data point (if it's being used to show Brady's number of interceptions is a trend with Arians).
I suppose the argument is that either Arians' offense results in an unusually high number of interceptions, or he asks a lot out of his QBs, whether they can handle it or not. I won't claim to have watched much of the other guys when they played for Arians, but I've seen most of the Buc's games this year, and Brady looks pretty similar to his last two seasons in New England. He's just older and being asked to do more.
It's not just pure volume though. Let's look at interception percentage.
Raw numbers:
Couch: 21 in 2001, averaged 9.2 in the rest of his NFL seasons*, an increase of 128%
Luck: 18 in 2012, averaged 13.0 in the rest of his NFL seasons*, an increase of 38%
Palmer: 22 in 2013, averaged 15.3 in the rest of his NFL seasons*, an increase of 44%
Winston: 30 in 2019, averaged 14.5 in the rest of his NFL seasons*, an increase of 107%
Brady: 11 so far in 2020 (on pace for 15), averaged 9.9 in the rest of his NFL seasons*, an projected increase of 52%
Interception percentage:
Couch: 4.6%, averaged 3.7% in the rest of his career
Luck: 2.9%, averaged 2.4% in the rest of his career
Palmer: 3.0%, averaged 2.8% in the rest of his career
Winston: 4.8%, averaged 3.0% in the rest of his career
Brady: 2.3%, averaged 1.8% in the rest of his career
So yeah, volume is a thing that contributes to raw numbers, but even the percentages are higher in every single case, and in a few, *significantly* higher.
One of the announcers said that Arians' offense relies a lot on post-snap reads, which you'd think Brady would excel at given his experience level. But maybe that's why a lack of motion hurts - it gives things away that helps the QBs, and by not using motion, your'e asking the QBs to interpret the defense more than other systems after the ball has been snapped - when a horde of defenders are crashing in around you. I don't understand how these things all work. I just know that whether you look at raw numbers or percentage, you've seen each of these guys in their first year in Arians' system, perform worse from an interception standpoint.
One possible exception is Roethlisberger, and he needs to be pointed out. His first year under Arians was in 2007 in Pittsburgh (where else?). That year, Roethlisberger threw 11 interceptions, when he averaged 11.5 in his other seasons, and had thrown 23 the previous year. But since you talked about volume, it should be noted that he only had 404 attempts that year, so let's look at int%. His int% in 2007 was 2.7, which is just a tick higher than his non-2007 career interception percentage of 2.6%. So he was obviously much more in line with his career norms compared to the other guys.