No, that link isn’t anything you need to worry about. Though it would be good to file an issue on openhab-addons (I think) to let the maintainers know about the broken link. I’m not sure it adds anything so it might be worth while just removing it.
That link is to the docs that the add-on uses, not anything you need to do. It’s just there for your information. The only thing you need to do on the Google side of things is documented under Google Assistant | openHAB.
In the past problems would occur if you tried to link to openHAB from Google Home and there were no Items configured so definitely set up at least one Item before following those steps.
As an alternative, you can set up Matter to expose your Items to Google Home. That would eliminate the need to go through two clouds. A matter hub (e.g. pretty much any of the Google/Nest hubs or speakers) will send commands to openHAB directly rather than sending commands through myopenhab.org. You must have IPv6 enabled on your network and at least one Google device with a matter hub on the network (you do not need a Thread Border Router). If you are looking to do this integration you likely have at least one (Prepare your smart home for Matter - Google Nest Help).
See All you need to make OH bridge Items to Matter for how to set up openHAB as a Matter Bridge.
Once the Items are in Google Home the original tutorial steps should be the same in terms of putting the Items into the right Home and setting up the home/away routines.