mandatory reconsideration notice for severe disability premium back date

My daughter moved out of my flat in February 2022, it wasn't until around July 22 that I realised I could get the severe disability premium of esa after doing a benefit check(I still wasn't sure) so I rang dwp to ask if I could claim it. I was told over the phone yes I was entitled to it and it would be added to benefit straight away. I asked if it could be backdated and they put a claim in for me. around 2 months later I learnt they would not backdate it. I put in for a Mandatory reconsideration. I received that this morning turning me down, saying It was a change in my circumstance and I should have notified them, they quoting the law regulations to do with this. I don't think I ever recall seeing these regulations on my papers when I get sent them. My question is, is it. worth me pursuing this further to a tribunal?