i dont understand why they need to know this?

maybe for a compensation claim?

i'd call a solicitor as i doubt its a legal requirment to fill that out, it'll be his defence team, as he'll be obliged to pay a compensation claim to you, but if its not caused you any financial harm he'll most likely get away with it

dont take my word as set in stone, but i think you not legaly obliged to fill it out, and i wouldnt either