Hi, you're completely right, and am working on a cleaner FAQ and changelog on the site. I fully recognise this is missing and needs improvement.
In the short term, for locks and alarms, they should be discovered by GH now, without any changes on your side.
The alarm is specifically the Domoticz Security Panel (i'm happy to look at additional integrations if people need them).
Both use the Domoticz Security Panel pin for two factor authentication, so someone can't just shout through your letter box to open the door

For extra security I don't store the pin, it's simply queried and then compared in the call.
Re: temp sensors - they should also now just work - currently there's no icon for a temp sensor, but they should now respond to queries.
This, along with the ability to query motion/contact sensors is the first step to notifications. These are in Google beta, and i'm pushing for Controlicz to be added, i had conversations during the alpha in Feb, so hopefully this will happen soon.
This will then provide parity with Alexa, where Controlicz can provide real-time notifications of sensor state change, to drive either notifications, or additional actions via Alexa. These require a level of trust from Alexa, and will therefore not be available via other options.