Steven
I have checked the legislation and there have been no changes to ESA in regard to a claimants commitment to attend WFIs and participate in Work Related Activity, if you are certain that you are in the Support Group then you are not required to do so.
My best guess is that the Decision Maker has taken a standard letter intended for WRAG awards and has used it to notify you of your SG award.
You will have to wait and see whether you receive a further letter, but I think it likely that you won't.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems