The OP is misleading you. You can run up a furnace to very high temperatures just by having a hole that air rushes through (with a fan, or wind). You don't need to reach 2700 to affect a steel structure - you can weaken the steel and produce strange unplanned loads at lower temperatures and cause failure cascades.
Not only is the steel weakened by fire (hence fire protection), fire warps structures such as trusses. First they expand and push out against walls, then they sag down. Trusses rely heavily on the geometry to carry loads. It's a cost effective, but sensitive structure.
The OP is misleading you. You can run up a furnace to very high temperatures just by having a hole that air rushes through (with a fan, or wind). You don't need to reach 2700 to affect a steel structure - you can weaken the steel and produce strange unplanned loads at lower temperatures and cause failure cascades.
Here is the NIST story about WTC7: https://youtu.be/PK_iBYSqEsc
Myles Power made a video about WTC7: https://youtu.be/7PpsCCTMP8w
I don't endorse him on other topics, but this particular video is good.
Not only is the steel weakened by fire (hence fire protection), fire warps structures such as trusses. First they expand and push out against walls, then they sag down. Trusses rely heavily on the geometry to carry loads. It's a cost effective, but sensitive structure.