Look closely. I'm viewing on an iphone and anything but a direct link goes to their mobile page
Empty cylinders used to be ok, then all cylinders were disallowed
There was a potential exemption for 'business contract customers'
I think you are seeing the 'restriction' on business customers with some allowance, but for private customers it's 'prohibited' and the wording may not be clear - look for compressed gas cylinders etc
Search through the forum and you will find people who have had their cylinders intercepted and confiscated
There was at least one guy who refunded the buyer and was trying to trace and get the bottle returned. I have not seen an update to see he was successful