Taking off work to do this, is absolutely great and i recommend it for everyone as long as you can. But whether something like cooking is a PITA, is mostly up to you and what you make out of it.
in 2008 I've took a seven month unpaid leave from my job to travel through central america and the caribbean. I never felt buying, cooking or eating was wasted time. Quite the contrary. Some of the most memorable moments of my whole journey came with those. Being it, cooking with people from all around the world in hostels, learning how to open a coconut and make a spoon out of the shell with a machete (yes, pretty touristy), or getting invited by a local family and let the kids show me how their favorite dish is done.
And I wasn't an avid chef before. I barely cooked by myself back home. Now i love it. Every step of the process. Its like programing – with real time compilation.
Yes, it is really time consuming. When I had other things to do, i just didn't spend that much time on it. I actually never had three meals a day (and i don't have now either).
I understand the statement and I find the idea of a having a food replacement in some cases very interesting. Its not anything new after all. But in my opinion, his motivation is questionable. Honestly, this Soylent-Shake thing remembers me of employers trying to squeeze everything out of their workers for sheer productivity. But, to each his own. If that guy is happy with his choice, he should continue doing it. If people blindly follow his way, its not his fault – they'd follow someone/something else. (As long as he is not starting a big campaign, saying that his way of life is the only right one)