Seller has offered refund but only if I close my claim against them

Description

Hi, a seller has offered a full refund if I close my claim against them. Is the seller able to refund once a claim has been submitted to Paypal or can they only offer a refund at the dispute stage as they claim they are unable to refund while a claim against them is ongoing? The seller is a large online retailer not a random ebay seller but then again, I was surprised in the first instance that I had to resort to a Paypal Dispute. They only contacted me after leaving them a bad review on TrustPilot.