That statement by Orser about Yuna isn't very surprising to me tbh. I remember in lots of interviews, esp those leading to to Vancouver (in those fluff/ documentary-like bits) - you have him recollecting at least in a couple occasions that when Yuna first came to him as a student, the first thing he (and I assume with David Wilson and Tracy Wilson) did was to make her 'happy'. I assumed what they did to help her discover the joy of skating instead of seeing it as a 'duty' like it's her job. And considering the early times when Yuna almost got sick of skating because of boots/ training/ injury issues/ dislike of competing - I assumed all this factors contributed to her being unhappy when she skated, and this was also presumably the state she was in when she first started training in Toronto.
And to top that I remember reading a translated excerpt somewhere one of the request of Yuna's mom/ team to Orser when he was asked to coach her is to make her a 'happy skater'.
The interesting thing about Yuna is that she rarely showed much emotion off-ice that you can't tell if she's just a really good actress on-ice, or just one of those people who keep things bottled up and bring it out when needed. (Then again, if she's an introvert, then they tend to be more inwardly introspective than lay everything out in the open). I remember a commentary by Peggy Fleming on her 2007 Worlds SP - that Yuna is 'very quiet-looking and emotionless during practice, but truly comes alive in competitions.' Tracy Wilson also remarked during 2013 Worlds that Yuna 'approached skating like it's her job' (as opposed to Kostner's emotional way of skating).
I think there was a time that joy in skating for her truly comes out, esp in in 2008-09 season, and the months coming up to the Vancouver Olympics. You can see it in her smile after each performance and in her body language..there was an extra spark to her that noticeably went missing in 2011 onwards (which, like others have mentioned was attributed to her finding it hard to find a motivation to compete after winning the OGM)