Hi - I did this holiday in 2016 - hello to Jaya, Bob and fellow travellers! Wonderful holiday, such experiences. Yes we did the river cruise in the small boats at night from the lodge, which was and still seems to be included - great experience.
However the sunset cruise now available as a separate, paid for excursion, appears to be something else - don't know if this is new this year? From the description it appears to go from Kota Kinabalu into the South China Sea - a totally different experience according to the description on the website.
Whatever you decide I am sure you will have a holiday to remember!