Hi Ed,
I sometimes use Google Earth as well for a quick overview, but a couple of days ago, I found out that it has to be handled with care.
One example: On my search for easy winter bonus points, DM/BW-235 is a quick catch since I don’t live too far away. Due to Covid, and since I didn’t have a valid reason for crossing the border without prior testing, I wanted to check if the AZ extends into HB9 and approach the summit from that side of the border.
According to the summit database, the summit’s altitude is 924m, so I set the flood level to 900 m (1m safety margin). Google Earth says YES. (according to this info, the AZ even extends to the inactive summit HB/SH-001)
Since I am aware that the altitude lines in Google Earth are not always reliable, I doublechecked with the official Swisstopo maps. Here, the picture is different: Looking for the 900m altitude line, I found that there is only a small area higher than 900m on the HB9 side of the border. Which would be fine if the summit altitude actually was 924m. However, the Swisstopo map shows a point with 930m altitude.
(Yes, I should actually take the time to ask the association manager if he’s aware of that). Funny enough: I have the official maps of the area in DL installed as an app on my smartphone. In higher zoom levels, the map indicates the summit with 924m. If I zoom in closer, the map changes and shows me the 930m point 
So in order to stick to the SOTA rules, the options I have is activating in DL when I have a PCR test done for something else, or when I have a reason to cross the border that qualifies for an exemption, or I’ll just wait until I don’t have to bother any more why and how I can cross the border.
Summarizing it, the flooding tool is a good entry point when preparing a trip and looking for convenient places to set up the gear within the AZ. However, I wouldn’t use it as a bulletproof evidence that I was in the activation zone. At least not without further verification on an official map.
73 Jens HB9EKO