The issue here is initializeBlock is not being fired as the condition type=owl-carousel is not being met for render_block_preview.
I had the same issue.
I currently have support ticket waiting, as type seems to the name of the the block registered by <?php acf_register_block_type(), but maybe there is something more to it.
In the mean time, I have removed the type parameter. Slight issue is that the initializeBlock runs on every ACF block loaded, but that is not a huge issue for me at this point.
Hope that is of some help, Joe.
