That's an over-generalization which is very often wrong. Massive timber (including things like CLT or Brettstapel) are very fire resistant and very safe in a fire. The outer layers tend to char while the rest of the structure is preserved.
To say more: if a large timber beam is exposed to fire and comes out charred, you can often just scrape off the charred part, but for a steel or concrete beam the damage may be fundamental (introducing cracks or permanently changing the size or material properties) requiring the part to be replaced.
