The fact the EPs are successful have absolutely nothing to do with PR approvals. EP holders are transient residents who are here at the whims of the current government and can be cancelled any time they desire. Therefore they can still afford to be lenient (relaxed) with those they let in for specific employment purposes at the behest of companies here.
On the other hand, PR is something that is "permanent" in theory and the liability passes from the employer to the Government. Therefore, it would, and does, cause the ICA to weigh PR applicants with a different set of scales than for those only applying for EP that normally only last for 2 years. And, yes, race can play a part. As does, marital status, whether applying with the whole family, family makeup, job history (job hopping?), Industry, education, age, and many other facets that we can only guess at.