"Reconstruction" step looks like a source of unjustified inefficiency: why reconstruct state by traversing proc and doing lots of system calls instead of capturing all data in the first place where it's much cheaper to do?
Of course, we create and update the state by inspecting the incoming stream of system calls.
We traverse proc only once, when you start a capture, and the reason to do that is collecting info for the PIDs/FDs that existed before we start the system call collection. That way, you can for example create a filter on the IP address of a socket even if that socket was created before sysdig started.