Help needed to clarify the difference between clearing cache app data or clearing data app

I'm having a debate with a close friend who insist that if I clear the cache off my device (LG Flex D950) I'm actually permanently deleting possible data on my device I'm trying to hide or get rid of. They insist that by doing so I'm removing cache from my device and transferring it to my pc. As a way of trying to hide it?? If I was wanting to get rid of it permanently why would I go store it on my pc?? If in deed I'm trying to get rid of it. My device isn't even recognized by neither of my two laptops since I rooted it. I've even tried restoring to factory settings and still can't sync to my pc anyway I'm getting off subject. They are convinced that somehow my cache on my device holds valuable information such as message call records etc. And have put it through their head that if you intentionally delete cache app data your deleting records and so on. Okay well as far as I know and correct me if I'm mistaken when you clear cache app data is harmless and is considered junk files on whatever device you might be using. Their only there to load apps faster like web pages or app you've used. Its stored files icons images that are pretty much useless.
Now I have read this to the person who is confused and clarified that if someone really wanted to delete all app data they can do so by clearing the app data which will restore your app to when you first downloaded and any settings or data previously stored would be replaced by the original settings and no user data. But they still insist that that's not so and it's the cache app data that does the whole deleting of records and manually transferred to a pc for hiding?? Please someone help...

The internet has a lot of valuable information as well as false. We all use it on a daily basis. But just bc you read something doesn't mean it's true. We're trying to pull up deleted messages but somehow whatever such friend reads online about deleting sms varies ways they have it in their head is what I have in deed done bc the msgs they want to see aren't being recovered. A lot has to do with the device being restored. But also when it isn't recovering something maybe it was never there to beggin with bc such msgs never existed period. But in their minds they are determind to find and explanation why it cannot be recovered.

No negative comments please I'm just trying to make the obvious clear to a friend.
Thanks in advanced
BY