This is a special post for quick takes by TsviBT. Only they can create top-level comments. Comments here also appear on the Quick Takes page and All Posts page.
Composite variables mask Amdahl. Suppose X has been going up. It's been going up continually, and a lot. And it's getting faster. That probably means X will continue going up. And, as far as we can tell, X will keep going up without bound. Right?
Well one issue with this is that X is probably a composite variable. There are probably underlying factors {A,B,C,...} such that X is really a measure of A+B+C+... or some more complicated function. The reason X is probably composite is that everything is composite.
If X is a composite variable, then X might be going up because each of its underlying factors are going up, or because some are, or because a sequence of underlying factors is going up in turn, or anything like that. So it's hard to tell what's really going on.
If there are general factors, then many composite variables may go up at the same time. That is, if A is an underlying factor for many measurements {X,Y,Z,Yuzz,...}, then if A has been going up, also X and Y and etc. will all be going up.
I am amused that you haven't actually named a function such that X doesn't escape all bounds just because A does. It exists, but it can't be modal if no name even comes to mind for it, right?