I have a completely new Pixel 8a that has not been booted yet. I was hoping to avoid configuring the stock OS with network access and just install GrapheneOS directly out of the box, but the guide says this:

It's best practice to update the device before installing GrapheneOS to have the latest firmware for connecting the device to the computer and performing the early flashing process.

Are there any part of the flash that will only be updated through the Google provided OS, so if I choose to install GrapheneOS directly, that part will forever be an older version? What is the worst that could happen, by not updating device first? Hope my question makes sense, I'm new to GrapheneOS.

    rtty0 Are there any part of the flash that will only be updated through the Google provided OS, so if I choose to install GrapheneOS directly, that part will forever be an older version?

    No.

      I recently did a p9pro xl install and noticed the guide said updating wasn't necessary since the GOS install would handle everything required. However my previous install a few years ago mentioned updating stock os prior to GOS install, so I repeated that to ensure everything worked flawlessly.

      If I understand correctly, getting to OEM unlocking will require a network check? So I think you'll have to end up with the stock device on internet prior to installing GOS. But I guess you could run the install once that is done, without any further updates done on stock. I always chose best practice approach for whatever it's worth.

      Graphene OS doesn't hold old updates within the web installer, everyone moves up when a new release is out to stable channel.

      You can verify it all with the verified boot key after install and even within Auditor so you see you're up to date.