I've only been a tourist in Greece, so definitely not an expert, but....
Take your house. Now add some scaffolding for a new floor on top of it. Does it alter the ability or even quality of living in it?
It might also help hide the pool, which is also taxed.
"Up to code" isn't the same as a safe house. That's just such an american way of looking at issues. All that does is make the legal liability clear. It doesn't make anything safer or nicer.
It's like arguing that a 'stop sign' makes an intersection safer. It doesn't. Real proper pedestrian and cycling infrastructure does. Traffic calming. A stop sign just tells you who gets bankrupted when another person is killed yet again.
Your asking the question 'if it's unclear who can be sued how can people be safe' but these things are completely unrelated. As any statistic would tell you.