The reply was about how drethelin's situation where a real situation/behaviour is repeatedly associated with imagined reward, is very similar to covert positive reinforcement where one imagines even the situation/behaviour itself. I'm confused on the relevance of mentioning the original comparison between actual/imagined reward in the context?

We have a situation where there are scientific/empirical tests performed on 'a real behaviour with real positive reinforcement' and 'an imagined behaviour with imagined positive reinforcement' that seems to support each other.

In fact covert conditioning does have the requirement that the patient imagine the situation sufficiently vividly. There's no reason to believe that if the patient imagine (or perceive) the situation too vividly (or too real) it would somehow affect them less.