In person, Willie was great to be around (I met him during one of his exhibitions). If Willie answered "I just got tired" when I asked him about what ended his run (especially if I were armed with foreknowledge from his book), I certainly wouldn't call the man a liar -- especially in the friendly way he answers the question in the video. I might upturn an eyebrow and smile at him with a knowing smile (and he would know immediately I knew a little more than I let on), but definitely not call him a liar.
-Sean
This is another one of those cases where you can both be right. Perhaps he got tired and missed the 6 ball because he wasn't concentrating. Maybe he got tired and missed the 6 ball on purpose. Ooh, wait, 'cause then he'd be a sandbagger! There's a good one. Would you rather call Mosconi a liar or a sandbagger?

Nothing's black and white like that. But it's still a fun thread to me.