Hey Mark, interesting observation. The reason for not resizing the flame graph and waterfall when the details panel is docked on the right the main content does continue behind the panel, the rational is twofold :
• When you dock it as a side panel, you're freeing up more vertical space to inspect things in the charts
• The panel, when docked on the side also becomes resizable and draggable anywhere. So you can resize/move it around if it's blocking your view anywhere.
Sidenote, the default position of the panel is at the bottom because we'd be adding a ton of enhancements here and we don't really want to encourage folks to use it docked to the side (that's how our current layout is and it inhibits us from adding a bunch of new things we want to there — plus that affordance also wastes a bunch of space).
Ideally if you undock it from the bottom, you should resize it to only show the details you want to scan through while speedrunning through multiple spans, and then expand it/dock it to the bottom when you want to look at one very deeply.