Valve engineer Jeremy Selan said that Steam Frame is a completely new product, which is why it got a different name.
This is a new development. We changed the name from Valve Index to Steam Frame, because we want to do something fundamentally new. We are trying to erase the boundaries between your game catalog and the device that allows you to run them. I don't want to impose on users in advance how they will use it.
The main difference between Steam Frame and Index is the presence of built-in "hardware" capable of running games independently. Index, on the other hand, was an accessory for PC owners.
Steam Frame was created to simplify VR. If earlier you had to configure the entire device to play on Index, now it is enough to put on the helmet, and the player immediately gets a choice of games.
Valve also confirmed that it does not plan to release its own project to demonstrate the capabilities of Steam Frame, which differs from the company's usual practice (for example, Aperture Desk Job for Steam Deck or Half-Life: Alyx for Index).