Not really. The result is kind of a letdown and that was too be expected, going after a single memcpy is low ROI because memcpy performance is probably what processor and library makers look at first.
What wins big is to remove useless stuff entirely. The demo boards I have seen often come with a standard Debian with all the services one might want for a workstation. The kernel is usually the same, with drivers such as PS/2 mouse enabled - thankfully just as a module, but disabling the useless drivers wins big in kernel compilation time. Which makes optimizing the rest a bit more comfortable (some options such as hardening and debugging can nearly full recompilation).
While there, one can also build the drivers one always want inside the kernel (not as module). A module inside a compressed kernel is loaded faster than from somewhere in a filesystem.
That said, Bootlin has indeed a lot of good stuff.
As for turning off systemd, it is not a bad idea if one replaces it with an init system that can start stuff in parallel (to mask the waiting times). I get that desktop users and admins like it a lot, but for an embedded system with a specific mission and a static configuration, it can overkill. There are a bit more caveats than what they say, though.