Hiura is simply a terrible example or comp.
Hiura had 300 ABs at the MLB level. His splits were extreme, his K rate was over 30%, and his BABIP was comically high. Not to mention he was a pile of crap on defense and his entire value was entirely offense. Despite some posters clamoring to lock him up, his demise was incredibly predictable. There is a reason he never got an extension. On the flip side Contreras has 1,000+ ABS at a premium position, All Star, MVP vote getter, and has Silver Slugger.
Hiura would have been 6 years from FA and still multiple years from even seeing arbitration. Contreras will make millions next year in arbitration. Actually, Contreras could falter offensively, have a major injury, and still carve out a career for the next 5+ years as a catcher...even as a back-up. Contreras is set to make millions in the future with virtually zero risk. Manny Pina's career lasted till age 36 and he made almost $15mil. The bar is stupid low for catchers.
Contreras is going to get generational money, that is basically an afterthought at this point. Unless you really want to cling to the argument that some catastrophic freak injury could happen. The risk is whether or not he makes $50mil+ in his career or not. Contreras can blow his knee tomorrow and the Brewers would pay him millions in both 2025/2026 regardless of performance.