Larian removing the headstart might be enough for Steam to issue refunds as they devalued the preorder.
I guess if anyone definitely doesn't want to play the game any more for some reason then they could give that a try and see if it works, though given that the free upgrade to Digital Deluxe edition for EA players (which included the 72h early access to Act 1) was announced as part of the announcement of the release date as 31 August and it's now 3 August it might be a hard case to make.
Not that I'll be trying, as there's no way I'm giving up my copy and anyway the extra goodies like the digital art book always seemed the main draw of the edition to me. I don't care about getting to start playing before anyone else, and I'd not want Larian to rush the game to me if it meant that there were more problems and risk to the release.