Can someone explain the therapeutic value of switching to one font family

How will being able to switch to one font family help? I really don't
understand it. What is the justification of this limitation in terms of
helping anyone. What family?

Again how does the ability to switch to one color combination help anyone.
What color?

Let's pick H.

How do either of these help users pick colors and fonts that lie outside a
small list provided by developers?

I can see ruling out ridiculous color combinations that don't have enough
contrast for visibility. I can see ruling out fonts with extreme dimensions
for the em unit (16px).

Now there are many sites that can handle 200% enlargement and break at 225%.

As stated I cannot see why a developer would not design a sight to enable a
change to one different color and one different font. What language
prevents that narrow interpretation?

Is that narrow interpretation it?

These SCs just do not make any sense.