SDT;
For years the same sentiment has come from the same corner of this industry; how can these, usually cadets, ever command when they've never done it before. Truth is, the system has been in place since the late 60s. Many senior C&T captains now at retirement, who participated in the first cadet courses could explain this to you alot better than myself.
My guess is, you have come from saab/metro/braz/dash or similar. The majority of operators in this country flying these types do not use this legislation in the same manor as the bulk of large carriers. That is: When an FO takes a sector, they are essentially in command, with the supervision of the skipper (Hence ICUS). As an FO, then, you are essentially training to become a captain on every single sector you fly. This is a much more suitable use of time, rather than being a support pilot throughout and forgetting how to command.
Of this real world command experience you speak of; If you call an extra 500 hours in a single pilot piston twin real world command experience, you are going to be hard pressed world wide finding pilots to fill seats. Who says that you need this to command a multicrew high performance aircraft? A handful of mostly Australians. I'm sure you'd cop a few angry looks, if you told all those who didn't have your real world experience before they took command, that they shouldn't have been allowed to. After all, these may be the very folk teaching you how to fly a particular type in the future.