They probably checked it with their lawyers and they were advised to just allow the refunds to avoid possible lawsuits. Plus, pretty sure Epic gave them way more than the total sum of the crowfunded money, so even at a 100% refund rate, they would still win money.
Also, does the PC version has the option for physical support? As in, a disk with the game not attached to a DRM service? Because if it doesn't, why bother with multiple formats?
The same reason any PC games have a physical release... err... I'll get back to you when I figure that out.
The disk is attached to Epic Game Store.
LTD: PS4 - 125m, Switch - 110m, XBO - 51m
2020: PS4 - 9m, Switch - 22.5m, XBO - 2.5m, PS5 - 4.5m, XBX - 2.8m