The problem with being continuously available is that it leads to "squeakiest wheel" syndrome where the loudest complainers get all the attention. Meanwhile, the quietly productive people quit because their frustrations aren't heard.

In my experience 1 on 1s are nice because it allows me and my boss to speak in private consistently. When we are both in cubicles it's hard for me to have candid conversations if I know everyone is listening. It probably depends on the person but I have always really liked one on one meetings.

It also establishes a pattern so that other employees don't automatically assume that seeing you and the boss in a meeting room means that you're having a candid conversation.

What is the difference between a one on one and speaking with your boss? I use them as synonyms.

Managers need to be available when things happen. I mean, they have other meetings, but during the day they should be able to give or receive "immediate" feedback; don't wait until the scheduled weekly (if you're that lucky) one-on-ones. However, if everybody is busy, and there's no immediate need to walk into each other's (virtual) office, it's good to have the scheduled interactions, to make sure you're still aligned as well as still pleasantly interacting as humans. (If the latter wasn't the case in the first place, maybe... wrong job.)

1 on 1s are not for feedback on day to day stuff. They are supposed to cover the more meta aspects not related directly to delivering on a daily basis. If your boss is using 1 on 1s to cover operational stuff they're wasting the opportunity to help improve the team wellbeing and progress.

I don't think we really had a disagreement, here. Just keep in mind that one-on-ones vastly differ between companies and managers, among other things in frequency.

In my situation, my boss is one of the 10 other people in the same office (when he isn't in meetings). All of us ask each other quick questions but try not to hold longer discussions there, because it disturbs everybody else. So more than that becomes a "one on one" in the discussion room. Nothing scheduled.

The presence of others. A 1 on 1 is private, but you can speak with your boss when others are present.

Or unwillingness to hire enough headcount due to being "lean".