An org can find ways to ensure juniors don't stay blocked while also ensuring that seniors can keep in flow state for long, uninterrupted periods.
Prioritize docs and tests. Teach juniors how to use docs and tests. Spread knowledge and mentorship around enough that a question on the team channel gets an answer from someone who is available.
All of these things have other major benefits in addition to restoring flow state for seniors—juniors learn faster, your tests are more comprehensive, seniors can basically onboard themselves, your bus factor goes way up. "Stick everyone in the same room" is just a local maximum, not peak productivity.
Prioritize docs and tests. Teach juniors how to use docs and tests. Spread knowledge and mentorship around enough that a question on the team channel gets an answer from someone who is available.
All of these things have other major benefits in addition to restoring flow state for seniors—juniors learn faster, your tests are more comprehensive, seniors can basically onboard themselves, your bus factor goes way up. "Stick everyone in the same room" is just a local maximum, not peak productivity.