Colour is a key affordance, and this font only makes it easier to achieve a good UX.
What mono color setting of the doughnut emoji makes it easier for my old mother to recognize the doughnot over showing one with multiple colors?
How does being able to specify the color for the empty / non empty battery symbols make it harder to achieve bad UX? At this point making it hard to achieve bad UX by UX designers should be preferred over making it easier to achieve good UX, as designers don't have the capability to do user testing on a huge variety of people.
The rest of us aren't forced to use XL sized text because some people need it, I don't see why emoji colour should be any different.
User interface I've seen use buttons for clicking, and the buttons can be colored, regardless of the emoji colors or lack thereof.
In fact, with black-white emojis, then, colored buttons get even simpler to spot.
So, the remark you made seems off topic to me.
I'm sad about your mother though, and father. I hope Google and others won't make the important buttons black-white-gray only.