Builder here, he's right, if you look at the reat elevation the chimney stack on the right is blackened, there was likely a fairly limited fire in the loft that damaged the roof, but by no means consumed it all.
The actions to put the fire out, water, pulling off tiles and battenwork would have caused a lot of roofing damage.
Rainwater and fire brigade water would very quickly set about destroying the place, plaster ceilings collapsing, paper and paintwork very quickly fail.
Judging by the interiors it was probably an elderly persons home, they either went into a home or to live with relatives, and the house was ravaged by the elements.
A bit of work was done at some point, the floorboards didn't make a run for it on their own!!
I'd say 4-5 years ago, no more, maybe less, in covid times, paint/ plaster/ mould etc happen very quickly - note the family crests picture in the loo, still in tack and the electric fire with no rust on it, its not been that long!
Brickwork and main timbers look in good nick, crew could strip it back in a week, 4 weeks to put a new roof on, then re-board/plaster, lovelly period property.
Sadly someone will bulldoze it and put in a cul de sac of rabbit hutches.