I just can’t imagine how I could stay in deep concentration and be “legit 65-70 hours per week,” unless I was also counting chatting on HN, Slack, meals with coworkers, research...ie the things that make my actual “work” time (of maybe 15 hours per week) truly productive.
I guess it would be totally reasonable to include some of those activities as “legit work time,” but then how do you decide what is and isn’t legit? I require a lot of adjacent “down” time to provide very high-value “on” time for my company, but how could you possibly know if 20 hours spent researching something you are excited about will have any value whatsoever for your company? Should it be “billable?” This is the unsung benefit of being a salaried worker: you don’t have to concern yourself about whether your research and exploratory development is “on task” or not, you just need to bring the benefits back to your company.