Good points and maybe expressed to generally by me.
I suspect who is laid off first is more to do with the lifecycle of the company actually, having been in high/low/negative growth environments myself.
I have found in negative growth environments, managers tend to get pretty sober about who is actually useful not just valued, and cut accordingly. Negative growth environments is also when more cuts happen, with generally a worse job hunting environment if you are cut.
But in frivolous times, yes, I've seen plenty of useful people get cut.. but they always bounce back better anyway.
The not valued column is let go first via the fact that the value function is what decides if their managers care or not