If the author spent a few months just working for some restaurant it could've helped him to estimate risks correctly and maybe stopped him from opening a restau

If the author spent a few months just working for some restaurant it could've helped him to estimate risks correctly and maybe stopped him from opening a restaurant at all. People with experience are much less into super-detailed business plans because they have the empirical knowledge. I suspect the desire to have a super-detailed business plan is a subconscious replacement for empirical experience.