Incorrect, steam allows for lower prices and give aways if steam keys you request... As long as it's not the base price. That's how humble bundle works. That's how every dev give away works.
The "devs" in this case want to sell access to the steam version of their game for lower than the steam price, on a permanent basis. Which is against steams rules, because steam provides a service that needs to be paid for, one that is worth far more than the 30% cut.