PayPal Offsite payment

Description

Hello,
I need to find out some information about an order and payment with PayPal Offsite.
I recently have come across with one web site where it is possible to pay with PayPal Offsite. If I want to make an order I should first make an order and after that complete the payment with PayPal Offsite. The seller will after a few hours (5 hours later – so it is stated on the web site) send me request for payment – invoice directly to my PayPal email address.
I am a little bit sceptical if this way I am still protected with PayPal Guarantee in case something would go wrong. For example, if I receive no package after an order is made can I report a case to PayPal to receive my money back?
Usually when I make an order the web site guides me directly to PayPal payment, but in this case the seller should send me request for payment after 5 hours, directly to my PayPal’s email address. Is this legit? Should I not make an order?
Thanks for any help