I should just add, that if a claimant is in receipt of any amount of IR ESA, even a penny, that the 365 day rule does not apply at all, no matter which group you are in.
Further, being in receipt of any amount of IR ESA can passport you to other things such as Disability Premiums, HB, CTB Support, free prescriptions/dental care.
I know what you mean about is saying on the paperwork that you are on IR ESA, but it is a generic paperwork typo, if you are in the SG and have pd your NI subs over the years you are on CB ESA unless you are entitled to IR ESA as you are below the means test and that bit you only get from filling out a form to ascertain financial means.
I had this on my recent SG letter from DWP, when I spoke to them they explained the generic typo. However I am still waiting for my £10 Christmas bonus which I should have as also being on DLA higher group indefinite for mobility and care.