I don’t know where to put this, so I’m probably in the wrong place.
When you want to add a wire in Eeschema, it wants to start running the wire from wherever my cursor happens to be. But when you want to run a trace in PcbNew, pressing shift-X puts you into the right mode, but it uses your next mouse click to figure out where the trace starts. Running a wire from the middle of nowhere makes no more sense than running a trace not connected to anything. Why can’t EeSchema be sensible?
Use shift+w to get the same behaviour as shift+x (notice something?) What you could complain about is that x in pcbnew does not start a trace unlike w does in eeschema (so maybe pcbnew is the strange tool?)
In 5.99 (i.e. in the future 6.0) these work uniformly and it’s configurable: either start drawing with one hotkey press, or only select the tool with the first press and start drawing with the second.