I like timeboxing many things. I like timeboxing work I don't know how to start. I find short timeboxes help me focus on the first thing of value. Back when I used staged-delivery as a way to organize projects, we had a monthly milestone (timebox) to show progress and finish features. The teams and I found that a cadence of one month was good for us. The timebox focused us and allowed us to say no to other work.
A cadence is a pulse, a rhythm for a project. In my example above, you can see I used a timebox as a cadence and as a way to focus on work. You don't have to use timeboxes to provide a cadence.
A new reader for the Pragmatic Manager asked me about scaling their agile transformation. They are starting and a number of people are impatient to be agile already. I suggested that instead of scaling agile, they think about what each team needs for creating their own successful agile approach.
One thing many teams (but not all) is a cadence for delivery, retrospectives and more planning. Not every team needs the focus of a timebox to do that. One team I know delivers several times during the week. They plan weekly, but not the same day each week. When they've finished three features, they plan for the next three. It takes them about 20-30 minutes to plan. It's not a big deal. This team retrospects every Friday morning. (I would select a different day, but they didn't ask me.)
Notice that they have two separate cadences for planning: once a week, but not the same day; and once a week for retrospectives on the same day each week.
Contrast that with another team new to agile. They have a backlog refinement session that often takes two hours (don't get me started) and a two-hour pre-iteration planning session. Yes, they have trouble finishing the work they commit to. (I recommended they timebox their planning to one hour each and stop planning so much. Timeboxing that work to a shorter time would force them to plan less work. They might deliver more.)
A timebox can help a team create a project cadence, a rhythm. And, the timebox can help the team see their data, as long as they measure it.
A project cadence provides a team a rhythm. Depending on what the team needs, the team might decide to use timeboxes or not.
For me, one of the big problems in scaling is that each team often needs their own unique approach. Sometimes, that doesn't fit with what managers new to agile think. I find that when I discuss cadence and iterations and explain the (subtle) difference to people, that can help.