That’s quite a leap from the definitions just stated.
In your terms, reducing the EAN would allow the Imagination Network and Salience Network to take center stage. As the EAN is explained, this is when we laser focus on a problem or activity. The outside world / retreating inward has nothing to do with it, going from your own definitions. The only definition to talk about the external stimuli is the Salience Network.
If we are to assume the definitions / set up is true, I would think that a better suggestion to unlock creativity would be inhibit tactical, execution-focused thinking (performed by the EAN), that way the Imagination Network and the Salience Network can come to the forefront. Retreating inward is not necessary.
In cognitive neuroscience, we have a location for the supposed EAN called the pre-frontal cortex. Different chemicals acting upon this area will elicit different results. Amphetamines like Ritalin will have a stimulating effect on this area thereby increasing perceived focus. Contrarily, depressants like alcohol will inhibit this area from performing it’s typical activity. This is why other articles have suggested that drinking a few glasses of beer can make a person temporarily more creative.
This fits with what you were originally saying; however, you took a different turn than what I was expecting and the reasoning for that turn feels lackluster and half-assed.
I appreciate using neuroscience to explain common phenomena and even help people develop positive, self-improving habits. Stay wary of how we interpret neuroscience research because it’s easy to misunderstand the research — what it's saying and what it’s not.