If the boss keeps sending emails on Friday there is no way that other people will really feel secure disconnecting.
Plenty of places with unlimited vacation cue or even pressure employees to take a minimum amount of vacation.
Edit: u/babycake's comment says it better: https://news.ycombinator.com/item?id=29879742
But companies know full well what they're doing. They know that if they replace guaranteed PTO with unlimited, not only does the employee take less vacation (more bang for the company's buck), but they also get to skirt around state laws on paying for unused PTO when the employee quits.
Plus, without any guaranteed PTO, companies can just decline your request for vacation any time. They can say they're in busy season, or they need office coverage, whatever. Whereas with guaranteed vacation, the manager would have a harder time declining those hours you earned due to bad optics.
Unlimited vacation without a guaranteed PTO base is a scam.
Yes i know some orgs can async everything. Some people prefer it. You could argue many cases on why async makes for a more mature interaction process, more efficient, etc. However we have not managed it. I'd say largely 50->80% of our communication is sync, and i don't see anyone advocating for changing that with us, despite having basically fully flexible hours and a global team.
On the semi-async stuff: If I am stuck with a task I probably can grab a coffee and eat a snack or check mails, but I would like to get some feedback soon, while I'm in the state of mind of that task. Else I switch completely to a different task, which has effort to come back on speed on the initial task on e the feedback is there. And if there is some clarification needed, it is good if all parties focus on that topic for a while, till key questions are cleared and everybody is unblocked.
Of course it is a balance.
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Edit
Since some of the replies seem to have missed what I was alluding to, I want to put here what I replied below:
Sprint goals are based on capacity, which is loosely defined by how much your team works. Defining how much you need to work by basing it on how much you should achieve, which is based on a number defined by how much you roughly work, is circular reasoning.
Look at what your peers with a similar level of experience are doing.
Look at what you're committing to do during sprint planning or 1:1s with your manager. (Assuming you're in a reasonable organization with a healthy workload.)
Anything above that is deserving of a raise or promotion.
Some jobs are process oriented in which the value contributed is in volume and efficiency.
>> achieve what I'm supposed to achieve
Other jobs are development oriented in which value contributed in defining the process or the end result of the process.
It seems like the former is more amenable to "regular hours" and the latter to great swings in hours spent in effort directly related to a specific purpose.
Specifically, Peter Drucker advocated for autonomy in knowledge work. However, this often leads to a lot of creep around meetings, Slack pings, and other context-switching activities. Cal, in the book, talks about the need to have good, organization level policies AND org-level processes to actively align to the work traits that the org needs.