This looks like it has a shallower learning curve to get started, but I would imagine that after a certain point it winds up being less productive to use the UI than to write code and this is ultimately why visual coding hasn't taken off. At some point someone will need to become a power user and be their organization's resident expert on Rainforest, but at that point they're spending all of their time in Rainforest and they're no longer a product owner embedded in the business.
At the end of the day the business owner should be writing specifications, the engineers should be using them to create tests and they each should be collaborating closely on both.