Yeap, it is indeed a new tactic.
Ihave seen all sorts of tactics appearing when other forumers lose argument and when they have nothing to say, such as "this is my last post" or "Ah who gives a ****, I dont care about the topic in the first place", or simply just digressing, or perhaps personal attacks or name calling etc etc.
Now this one about not being serious and not accurate, that takes a new high. That effectively now means that we cannot take anything he says seriously Since after all, he isn't serious nor accurate.
But wait, next he'll say that he's 99.99% serious and accurate - after all, he did say "not 100%".