Not doubting you at all -- it just seems to me to be a standardised bit of twaddle that they are churning out.
I wouldn't expect them to give a go-ahead to re-use jars (way too general, way to open to difficulty), but if a jar is indistinguishable from new, then its, errr, indistinguishable from new?
The reason (twaddle) they all say that you cannot re-use jars has nothing to do with safety. It is to do with the law.
If you supply food these days (whether packaged or a pasty served hot in a restuarant) you have to be able to trace and document every aspect/ingredient from cradle to grave.
For instance when I take a delivery from a van driver, I am supposed to inspect his temperature sheet so that I can prove that the goods were delivered at the correct temperature before they are transfered to my properly recorded fridge before they are taken out and cooked and place on the plate before the customer (and probed along the way about three times). This same paper trail has gone on from the farmer to the producer to the packager to the wholesaler to me.
Of course in real life the van driver is running late so runs into the kitchen and just throws the food onto the counter and runs out the door, while the kitchen is in uproar and filled with smoke and flames as we have just burnt the toast for the umpteenth time, so the d####### delivery gets forgotten about for 10 minutes and ends up in the fridge after the uproar has ceased. Is it at the right temperature. Of course it is - it is deep frozen! It will take me all day to de-frost the bacon for tomorrows breakfast. Can I prove and document it. NO. "Chain of custody" is broken.
You can only use honey jars that have been manufacturered, recorded, shipped to Thornes/Maisemores/whoever, who recorded proper storage, handling and then passed to a recognised courier so that the paper trail is maintained. If you use re-cycled jars and clean them and fit new lids, you have no paper trail. Ergo you cannot prove that they have been safely handled and the legal case is wide open. Buy them from Th##### and they arrived half smashed with tiny fragements of glass in the remainder which you do your best to clean out. No problem, you are legally covered, you have a paper trail.
It is the same reasoning that sends EHOs round to old ladies kitchens to inspect them when they bake cakes for the Womens Institute coffee mornings. How many people died of food poisoning from a WI cake. None I would imagine. How many people died from food poisoning from properly documented butchers - quite a few in Scotland a couple of years ago. They did everything wrong but had the right paperwork.