50 hours ICUS is more than likely an insurance requirement, often for those who do not have sufficient experience in a similar type. Some insurance requirements may require more, and/or a set TT, minimum hours of IF, multi etc before you're insurable on type.
Some requirements are sometimes waivable by the insurer, often at a cost! Think: putting an 18 year old male P plater with 6 speeding fines and a drink driving charge on your $120,000 turbo-charged sports car's insurance.... then add the "aviation premium" and up the insurable value 10-20 times!
I'm hoping in your extensive searches you've discovered the differences in fuel planning requirements, found out if the aircraft is RVSM and read about the regs to go with that, memorised all the Cat B speeds, know what's required to operate in class A airspace etc