What you should be worried about is how PayPal does it tho. Since they never let you withdraw to personal BTC wallet, their "BTC" might actually be non-existent coins created to inflate the market artificially. Especially since their terms and conditions clearly mention that, as a customer, you are not holding any specific recognizable cryptocurrency on their platform.. so what are you holding exactly? Just a number
PayPal, as a public company, would be making a potentially business-wrecking move by not pairing user crypto purchases with actual crypto. If they were "faking it" they would be on the hook for funding the difference when the price rises out of their own pocket, and with an asset as volatile as bitcoin it would be extremely risky. So on the face of it, I would severely doubt they're faking it because there are only downsides to doing so. Further, they have said that users will eventually be able to withdraw crypto, so that wouldn't do that if they didn't have the coins to back it up.