Why is that reasonable? Storefronts don’t get free keys from Steam, they have to buy them. After they pay Steam, they should be allowed to sell them at any price they want.
Imagine if Ford said you couldn’t sell your car for less than what Ford dealers charge for used cars.
This is the easiest way. After installing the game, Heroic even has a command that will add it to Steam (with artwork IIRC).
My sort of interesting experience:
I tried to buy the LE on launch day, and couldn’t get through the payment page. When it was listed as sold out, I bought a regular deck without much difficulty.
Then I saw the LE was available again, and decided to try to buy it again. I was planning to cancel my original order if I could get the LE.
I tried to check out dozens of times over the next 24 hours, but on the final page I kept getting the “something went wrong” error.
About an hour ago, I decided to cancel my original order (you can do this by requesting a refund on the order page). The refund was issued 15 minutes later.
I went back and tried to order the LE again, 30 minutes after the refund was confirmed. Went through on the very first try.
So from my limited experience, I think Steam might be blocking all LE orders (and maybe even regular deck orders?) if you already have an active order.
Because those other retailers already paid Steam for those keys.
If Steam doesn’t want to compete against third party key retailers then the solution is not to sell keys to third party retailers. Once Steam takes their money, they have to accept the competition.