I would rate it a bug because I noticed the following:
1. I create the table manually
2. I manually insert a code block with line breaks
3. I look at the result, I see the line breaks in the code block
4. I click on edit below the table (start edittable editor)
5. I change nothing, just click on save
6. Looking at the code block again in the manual editor shows that the line breaks were removed
So I think this is a bug as I would expect that editable does not change the content. It looks like there is already a similar bug report in the edittable plugin's issue tracker, see
https://github.com/cosmocode/edittable/issues/134.