I have the same thoughts, so I also gave my vote for this.
There are rare cases when a button should be 100% in width by default, as it currently is with “display: flex”.
It works well when the button is wrapped in a div that has “display: flex”, but not always do I want an extra wrapper.
When the button is used alone, I frequently find myself changing it to “inline-flex”.
So I agree with @yankiara that the default for buttons should be "inline-flex.
This is a good point and completely valid, thank you.
Changing this could unfortunately cause issues with installations that rely on this particular display property.
We’re currently reviewing the defaults system and I can see that this is where this type of setting would be perfectly suited.