I appreciate your dedication. Never once in my career have I been at "I'm so locked in, I can't spare a single second of time to look at another monitor" level of concentration :D
The point is, there's no clock in any other monitor because the top bar is only on the main one.
To me it's not about a couple seconds that takes me to look at my phone. It's the inability to have it on all my monitors just like all other DE. And it's not only the time. You can't access your notifications, your app indicator icons or anything you add to that top bar through extensions.
Sure - I get the point, but also have never found the top bar on another monitor to be super prohibitive to my production. It's rare that I don't have a spare moment to move the mouse to check notifications (in fact, if they were close to my full-screen work environment, I might be tempted to check them MORE frequently).
To me it's not about a couple seconds that takes me to look at my phone. It's the inability to have it on all my monitors just like all other DE. And it's not only the time. You can't access your notifications, your app indicator icons or anything you add to that top bar through extensions.