The fact that there’s no rendering on dev means it’s not a proper sandbox. Yes, you can play with the editor, but you can do that with the real map by just not saving your edits. It’s not always easy to understand how it all fits together without going through the full process and seeing the result.

The walkthrough is a useful tutorial but it doesn’t cover everything one might possibly do (or wish to do).

Which is why I think the google engineer (if he actually is one, which may not be the case) was using his own location as a mini-sandbox to get a feel for how everything works. As long as he reverts his changes relatively quickly there’s no real harm done.

It occurs to me that various GIS apps (for many different mapping systems) over the years have been programmed by people who treat undefined co-ordinates as zero (or program using languages that coerce undefined values to zero). The has resulted in an accumulation of junk at 0 north, 0 east where there is no land. Is there a case for us planting the mythical island of Erewhon there as a sandbox? Probably not a good idea for two reasons: newbie mappers wouldn’t know it was there and consumers might find it and assume it was real.