cadayton Well my focus at the time was on the phone's Fastboot Mode interface
The docs provide an explicit "Press the button below to start the download:" above the Download Release button. I don't know why the texts before the buttons are inconsistent, sometimes ending with a colon, sometimes ending in a period, sometimes a direct command to press the button. An explicit "Press the button below to ..." on the first button (or maybe all the buttons?) rather than just the second option might have gotten your focus shifted?
cadayton [...] so I did have to resort to using the CLI
I assume you meant "didn't". The standard admonition in chat is something along the lines of "don't skip steps, don't add steps, the web installer instructions don't mention adb". Perhaps the doc could benefit with something similar but slightly more tactful.
cadayton Had I known from the get go to implement the eSim card on the stock OS before installing GrapheneOS
In general this shouldn't be necessary. Only for those providers which can't provide QR codes and/or need a special app to activate or manage the eSIM options and that app doesn't function correctly with GrapheneOS should this be a problem. Could you provide more details on which provider and where it went wrong for you?
https://grapheneos.org/usage#esim-support