I also wanna add that when they say "exclusive pre-order bonus", it's just clever marketing. People fall for it.
Read that statement as: "bonus (a.k.a additional/free content) that only comes with a new purchase if you pre-order it. if you buy it on day one without pre-ordering you will not get the bonus."
it does not mean "exclusive content our company spent payroll hours working on that we just wanna hand out for free to the few people who pre-order and never try to make money on the content at a later date"
You're just being a cynic... = /
Realistically they mean exclusive early access now. Just a year or two ago exclusive DLC was just that... But it's hard to offer that now, especially with community games - most of the time people demand that it all be released again (usually for a small price).
So we exclusively get it early and exclusively get it free... Why people who didn't get that particular pack have to pay for it later.