kanban, deliver something when it's done (even incremental when possible), fast feedback...
The notion of "here's what we'll do in the next X weeks" takes a certain amount of planning which (imo) is often better spent just doing first. As/when issues/questions come up, they need to be addressed then, not waiting.
You surface the problems early by some planning, then some work, then some feedback. "Sprint boundaries" don't seem to help in any of that. They help other people who want to know when something might be 'done', but it doesn't help me get feedback or clarify misunderstandings any faster.