With everything being web-based, I imagine the magazine workup is zipped over the network to one of the European facilities and fed to the presses, collated, stapled and shipped to customers in a matter of days.
Many of the big newspapers in the US were contract printed like this, too, so the NY Times might be sent to the production plant of the LA Times by wire, printed and distributed overnight.
I have to say i was rather impressed too. This is only the second issue of my subscription (the first was sent in a plain brown envelope from the US and I received it a week or two ago) and I rather expected to be lagging behind things here in the UK with the postage etc but possibly this won’t be the case. We’ll see.
I have noticed that I’m tending to skim the online version and just reading anything that particularly catches my eye, whereas I read the hard copy much more closely when it arrives. Probably a sign of my being old (although quite a young railway modeller by Wall Street Journal standards) and regarding Kindles etc as an abomination to be scorned!
I very much prefer reading real magazines to online versions. I can take a magazine to the bathtub, the beach, the tree stand or the doctors office without worrying about my tablet getting wet or stolen.
And it’s just easier to read than paging through a computer screen. Millenials probably don’t think so. They don’t read books either.
Just as an addendum - I took a better look at the magazine that arrived this morning (the May issue !!) and it was posted from an address in Essex (so between 10 and 50 miles away). So I guess MR either ships in bulk to the UK and posts locally, or prints locally and posts from Essex. Still, I’m impressed - I’m getting the hardcopy about a week after the electronic edition goes up on the website.
Even here in the US, the time for receiving a particular issue can vary greatly. It’s not unusual for someone on this forum to reference an article in the “new” issue of MR a week or two before I receive my copy in the mail. Apparently some people receive their issue after me. Not sure if they do bulk mailings to different regions at different times or, as the OP suggested, perhaps they send the information to different printers in different areas who create and mail the magazines.