I have no idea about that.
My cousin’s neighbor in Celebration is an Imagineer for WDW. He actually used to work at Universal/Islands of Adventure, designing rides for them. Then Disney found him, and he became an Imagineer.
I don’t think an Imagineer would get fired for brainstorming rides that are too scary. However, after dining with an Imagineer, I learned that Walt Disney Imagineering goes through a lot of lay-offs when there’s not a big project. If their specialty was rollercoasters, there may not have been a need for them. Also, they could’ve just wanted to move onto more intense rides that didn’t fit into Disney’s “family-friendly” theme parks, and chose to move to Universal Studios.