First, this is a story about an unreleased and unannounced product. Second, I really don't think Apple is intentionally trying to harm its customers by allegedly making the (unannounced) wireless charging feature work slower. Perhaps this is an engineering trade-off meant to ensure safety or a better customer experience. Apple can't do anything without people whining. And it's often about the stupidest things!
There is an engineering trade off, and it has nothing to do with the actual ability to transfer the power but rather the battery. Faster charging will almost always cause some level of battery degradation. Although small, Apple likely has their battery chemistry keyed in and does not want to deviate to much from the conditions it knows works best.