It really depends on who you consider the "many" to be. I've seen people who claim they can meaningfully iterate on 10 projects simultaneously, and I'm skeptical of that. My personal experience is that my decisions are noticeably degraded at 3-4 parallel workstreams, and with even the simplest projects I'm non-functional past 6.

But I can juggle 2 workstreams in a day easily, and I can trivially swap projects in and out of the "hot path" as demanded by prioritization or blockers; before LLM coding both of those were a lot harder.