Infinity saw don't break the wood, but instead it gives you normal things from it.

Version : 0.4.3

If you keep going with it will bring down the whole tree. I think it works like the enchant 'smartass' from the old days. I.e. it takes from the top and gradually works down to you. At least this is the behavior i observed when working down a warped tree in the Nether today.

It is a bit counter intuitive, does seem to give you random blocks related to the tree and doesn't work with Ultimine AFAIR though. Likely something maybe addressed by our friends in InnovativeOnlineIndustries or maybe in the quest?

Ok, it's cutting down the leaves in a bigger area, the quest was saying "can chop increasingly large area" so i tought it's a bug.