I completely agree with you. In particular about the sacrifice everything misconception. Ash Maurya goes even further into suggesting Keep your day job[1], until you reach product/market fit.

Nevertheless, I am always wary of absolutes. Some people can't wait, and not going all in is very harmful for them. Some people have a lot to lose, and cannot afford such approach. As always, context is king.

[1] http://www.ashmaurya.com/2010/03/bootstrapping-a-lean-startu...