I think it's an official request, as it's last day of the ETA + 30 days. If the buyer received the item within a few days but it had an ETA of 1-2 weeks (common these days, due to extended handling times and ebay accounting for longer delivery times as well), then 5 weeks after receipt would put it right on the cusp of eligibility.
OP - Do you have an option to decline the request? I got one (an item not as described return request, that is), last week where the original purchase date was over 2 months ago, and for the first time there was actually an option to decline because it was no longer eligible for the MBG. If you don't have that option, then eBay will probably enforce the request for the buyer unless you can argue successfully that either the purchase is no longer eligible (check the exact dates if you can), or there is other evidence you can provide that the item was received in as described condition (eg positive feedback, or other communication from the buyer).
If customer service can't assist, the options are unfortunately very limited, so you'll need to be prepared to arrange for the item to be returned (there should also be an option to offer a partial refund, sometimes - as grating as it is to even think about when you suspect the buyer is taking advantage - this can be a good option to avoid a return and full refund, but you'd need to communicate with them first to ensure they would accept this as once an offer has been made, if they reject it you'll have to move forward with the return process).
