I guess Kickstarter exclusive is not that exclusive.
Most of those KS cards are actually year one promos, and not KS-exclusive at all, never were. They are being gradually released as part of Epic's prize support cycle, and you can already acquire a few of them as tournament prizes. This was all explained at the time. A handful are KS-exclusive art only, and will be re-released with different art in the future. Being as the Hero Realms Kickstarter is a Kickstarter, though, I'd still call them exclusive to Kickstarter?