What is the time span in which this research was conducted? It is possible that someone under the control group could progress slower (due to complexity) but more surely over a longer period of time, for example.

Regarding "can" and "will", I theorize that saying "will" implicates 100% confidence but it doesn't necessarily mean our minds will truly believe or feel that confidence. If I think back in my own personal experience, I've told myself for hours before going to sleep "I will lucid dream tonight. I will be aware that I am dreaming." but it never happened, and maybe each time after I subconsciously dwindle in my expectation. In the book A Field Guide to Lucid Dreaming, it is suggested that thinking in present tense is the best way to eliminate doubts that your affirmation will come true, "I am lucid and aware in my dream".

Some people are auditory also, so I wonder if listening to a track on repeat saying "you are aware that you are dreaming" would help those types of people.