You don't seem to know how paypal works, or have any/a lot of paypal experience.
If people are saying that you should not use paypal for buying btc, it is because paypal transactions are irreversible, and not btc transactions.
I'll assume you meant that they are
reversible. And as a matter of fact I do have quite a lot of experience with PP, especially in regards to BTC. I was here when the scams actually started...
Finally, the fact that they are reversible is only part of the issue. If PP actually went to any means to verify whether the "goods" being BTC were actually sent and didn't always side with the buyer we wouldn't have an issue. The problem is that PP doesn't bother, and hence they simply reverse the transaction and the seller gets nothing.