But launch feedback is, and has been for years, displayed in non-blocking ways on many other platforms (including progress bars). The only advantage I see for full-screen fixed-duration animations over these is that the non-blocking indicators actually indicate -- they show you that you are waiting for some long operation to complete, and that makes the device feel slower.

When everything has the same lag, and a uniform visual distraction is used as cover, efficiency is lost, but users (especially those who don't know/care what goes on under the hood) will not have a perception that the device is slow.

To me, this is a bad trade-off, as I want to use a device, so reality matters. Manufacturers, alas, have a strong incentive to make this trade, because they want to sell devices, so perception matters.