ColorFunction seems to various stylistic changes in Plot (and probably other plot-like graphical constructs) relative to PlotStyle. Here's a fairly minimal example:

plota = Plot[1, {x, 0, 1}, PlotStyle -> Black];
plotb = Plot[1, {x, 0, 1}, ColorFunction -> (Black &)];

Here's plota:

And here's plotb:

It may not be obvious how different these are, but running them through ImageDifference yields this:

And here's an animation which switches between the two every second:

As you can see, in b the vertical axis shifts left, both axes pull away from the image boundary, and get thinner, the ticks on the axes get shorter, the axis labels get smaller, and the graph of the function gets sharper, among others.

Is there a way to force these changes not to happen? Sometimes I really need to use ColorFunction, and I'd really very strongly prefer those uses to be consistent with others (for example, this is absolutely essential when I'm stitching together two animations; my current workaround is to use ColorFunction in place of PlotStyle even when I don't need it, but this is confusing and ugly).

Of course, even better would be for this (presumably unintended) behavior to be fixed, but I realize that's probably hard.

(Though not exactly the same, similar phenomena happen both on my Mac Pro (late 2013) with Mathematica 12.2 and on my MacBook Pro (13-inch, 2016) with Mathematica 12.0. The images above are from the Mac Pro, since it's on the latest version of Mathematica.)