[Pow!]

^hm I think it's not about which one to believe (in your story case) because in the concert they indeed lipsynced for some of the dance songs for some reasons.
Why did I said some reasons, it's because us fans still don't really know the exact reason why they did that. We all know that they're more than capable to sing those songs live (like Genie and all those songs they've performed live before), and there must be some reason why they didn't in the concert. Was it because the concert was 3-hours long, with 32 songs, and because the dance moves are exhausting, etc etc there are tons of reasons that could be think of but we don't know for sure. What I know is that for the ITNW Tour, SM said that they didn't performed some of the songs fully live because they wanted to focus on the dancing. Was it still because of that? Maybe.

A skeptical person may think of them as excuses (and yes they are excuses) and said that the girls are lazy, but us fans should know better than that. Just believe in them and try to understand. Negative thoughts appeared because sometimes people just refused to understand.

I think what silis meant to clarify is more about the lipsyncing on tv performances accusations since we've seen the real deal behind Hey3x performance. Because if you think of it, why they only did it in Japanese shows while they almost never did it in Korean shows? And moreover they're just starting their career in Japan, so why they must ruin their reputation? As a rookie in Japanese music world, of course they don't want to get a red mark for their report card, thus they're working hard to get a good impression. People just have to sit down, relax, and just calmly think about these things before thinking negatively. Negativity is bad for health.