I do wonder if they look at your overall history – eg I get quite a lot of gift payments but also pay for a lot of things at shops with paypal so overall, they're still making money from me so maybe they're not as bothered.
OK just checked – I've had £903.25 come in the weeks up to the email from them
2 of the payments were gifts, 1 for £70 & one for £15
Maybe I was just unlucky & I fell foul of a random check?
I've since sent gift payments but not received any
they probably searched the comment boxes on all gift transactions and the ones with addresses and details of what the payment is for. were red flagged then nice emails were sent.