Earlier quoted context omitted.
The user perceives lag after 300ms So write efficient, responsive software. If your screen doesn't engage the user while it's making the switch There are many ways to "engage the user" without wasting cycles on animation. If your software performs so slowly, why exacerbate things by burning cycles on animations?
Not all things are about speed. Helping the user to understand the "story" of what they're doing is just as important. Most UX kits involve transition animations for this reason.
Are you kidding me? You just wrote:
The user perceives lag after 300ms, and switches thought in less than a 1000ms. If your screen doesn't engage the user while it's making the switch, you risk them starting something else.
That was the entire premise of your prior comment. Any other points you want to hop to?