Stuck bullets is one issue. Small charges in a large case is one that can result in a big surprise. There are methods to circumvent such things, but it is not as simple as it might seem to a rookie
What I find interesting is wives tales that live on and on. I agree 100% about shooting the wrong reduced load no matter the bullet material. Stay within reasonable loading guidelines and things will be fine.
What seems to a lifetime ago, I helped a couple of gentleman test early versions of what became the Cutting Edge Bullet Safari solids and Raptors. Back then we called them BBW 13s (Bastard Bullet Works) non-cons. That I know of I killed the only Cape buffalo with an early copper non-con which became the brass Raptor.
We did much of the testing to dispel the myth that monolithic solids damaged double rifle barrels which was the “belief” of many DR snobs until Woodleigh started producing one. Also much testing was done to determine the best meplat design, number of bands, and material.
Keep in mind I played a small role compared to the other gentleman, basically they sent me bullets and I loaded them to various velocities, fired, and recovered the bullets, reporting straight line penetration and other observations.
After all the above bs I just wrote one of the things my buddies did was to buy a strain gauge to test strain on the barrel, I think 5 inches from the muzzle. All types of bullets were tested. Guess what gave some of the highest readings, hard cast lead bullets with gas checks and soft cast lead with no gas checks. They surmised the lubricity of brass was butter than copper and lead.
At the end of the day, in bullets that really matter for hunting, there is far more to pressure or what may get stuck in the barrel than whether it is lead or copper or brass.