In my case, I rarely include a callout header (e.g. > [!info]) at the start of the block and that seems to be what results in my table looking rubbish, like this:
Well, a callout is a block quote with a callout header, and you want to remove the callout header?! Then you’re left with a block quote. It’s not a callout anymore.
On another note, if you search the forums you’ll find plenty of CSS tricks related to changing the appearance of a header, and I reckon you could use that to visually hide them, but I still don’t see the bug.
So if I understand correctly you want your table to be rendered with the look of a blockquote (border on the left only) in live preview mode.
You’ll have to use a custom callout for that.
Here’s a custom callout css snippet that you could use for this: