I wouldn't say it's scored more harshly, it's just that they are doing more in each level, so there are more deductions to be had. The exception to this is platinum beam - we think it might be slightly easier than gold in certain ways! Because if a platinum does a round off on beam, they don't have to do another acro at all, but a gold who does a round off would still need another skill. We do usually prime our new golds for this especially - they're not going to be getting 9.7s right away now that they have to do two beam acros, go to the high bar, and do more tumbling.
The one difference I can think of off the top of my head is that in silver and gold, a pause on bars is a 0.1 rhythm deduction that judges can use their discretion on taking, and in platinum and diamond it is 0.3 every time, so in that sense, yes, things are harder.