I'm inclined to agree with that. While, as you say, nighttime on Dagobah doesn't in anyway have to correlate with nighttime on Bespin, it helps the film dramatically to have it play that way. It's just easier for the audience to accept that flow, because our own very simple clocks work that way.
And let's face it - and there is obviously no empirical information in the film to support this - but it just looks and feels like sunset, not sunrise. In the theatrical version, yes, the pattern does seem to indicate sunrise, then bright daytime, and then ending with the escape at sunset, but it just doesn't feel like sunrise.