I take reliability data with a grain of salt now that I have a bit better understanding how those stats and failure rates are determined. I work in a different industry (power tools) but I'm in the tech service department and work directly with the guys that calculate all of our product failure rates, warranty claims, etc. and that's done very similarly in all industries that have similar structures (as in a dealer network selling to end users). Imagine you have a product, say a motorcycle, that has a 50% failure rate. Many would say "holy crap, that's an unreliable POS!" , but the fact is every single failure is counted in the stats regardless of what it is. So on this motorcycle model that has a 50% failure rate it means that if they sold X amount of motorcycles, there have been X/2 reported failures...it could be that the warning labels fell off the swing arm on half the bikes they sold, or that the screws that hold the license plate fell off on half of them. Little things like that count as failures if reported by the dealers. But does that really mean the machine is bad? No. You'd be amazed how many "failures" or warranty claims I've seen from some of our battery products because supposedly the battery doesn't last long enough, when in fact there is nothing wrong with the product and the battery lasts exactly the amount of time we specify, but people are too lazy to look in the manual so they think there's something wrong lolIt's probably more a case where a few bikes go wrong and the story gets spread around. And even then, it may be a matter of degree rather than a contrast of trash and treasure. But when a YouTuber like CycleCruza has problems with a Ducati and tells everyone that he wouldn't own one outside of its warranty coverage, the brand's reputation takes a hit.
Reliability rankings often put the Big Four at the top and many European manufactures toward the bottom. For example, this came out recently (admittedly, on a more entertainment oriented website): Ranking The 9 Most Reliable Motorcycle Brands Of 2020 (And The 6 Least Reliable).
Also, in an older owner survey from 2015, Consumer Reports said: "Consumer Reports’ survey of our subscribers shows that the Japanese brands are significantly more reliable than most bikes from other regions—led in order by Yamaha, Suzuki, Honda, and Kawasaki. Domestic brands Victory and Harley-Davidson were midpack, and Triumph, Ducati, BMW, and Can-Am were the more trouble-prone brands. " See Motorcycle Reliability and Owner Satisfaction - Consumer Reports
So I think there's something to it, but the difference might be exaggerated in the public eye.