Yes, deliberately so. When the cart changes, the bar's new message is read out politely by a screen reader, through one announcement area the page keeps for the purpose; the progress track is a real progress bar with its current value; the dismiss control is a proper button with a name and works from the keyboard; a floating bar never sits over a link that has the keyboard focus; a bar waiting to appear cannot be reached until it shows; and the celebration animation stands aside for anyone whose system asks for reduced motion.
The settings screens are built the same way: every help line is read out with its field, and groups of choices have names.
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