Yeah this is weird. I know lots of people that PREFER bumpers. As you said, they can cause more bend in the bar, which tends to make deadlifts easier. Also, they rattle around less so sometimes they feel better on the joints. But metal plates feeling easier? never heard of that. All I can think of is that the metal plates are a different size (which you said they're not), that they are a different weight, which could be (even though it's weird), or that you just have a mental block.
Either way, they always use metal plates in competitions that are not crossfit lol. So you should be fine.