Forensic is a strict science and we should let the evidence speak for itself.
Several months ago I still could recovered Line deleted chat messages as below:
Last month Line 5.3 added new feature called "True Delete" can wipe deleted chat messages. "Wipe" means zero out and those deleted chat messages will no longer exist. Now my Line version is 5.5.1, let's see what will happen.
Look at "Blocks containing deleted data", those deleted chat messages were wiped and so we can do nothing about wiped data.