yes they have emailed me a pic of the offer, I checked my pro shop and it was only yearly.
I believe this is just one of those things that differs between mobile and PC. AFAIK, PC has never had any option but the annual subscription, and I did notice that monthly option on mobile the other day when I was poking around the newer interface.
I really don't understand why some people feel they need to make sideline comments that do nothing to answer the original question(s). I find that most people can decide for themselves how they want to spend their money/credits.