NO IT WASN'T, Jocko. Your sources are lying to you. The FLOOR SUPPORT TRUSSES WERE NOT ENCASED IN CONCRETE!
That was one of the design innovations of that building to keep it light weight so it COULD be built taller with no internal columns breaking up the floors between the central services column and the curtain wall. The trusses were open and visible above the false ceilings. Metal floor pans were mounted on the main trusses and a light rebar grid was built above that and then a thin concrete floor was poured. The concrete floor is not "structural." The only structural use of concrete in the building was utilized in erecting the central core and pouring the foundation. Here is simplified floor schematic of the World Trace Tower's design:
World Trade Center Floor Schematic
World Trade Center Building One with Trusses up to floor 37 sprayed with a
thick asbestos based anti-fire insulation
World Trade Tower Building One (above 37) and WTC all of Building Two show
much thinner non-asbestos anti-fire insulation or none at all.
Note that the bridge girders ARE NOT ENCASED IN CONCRETE.
This is why I called your sources the "tin-foil hat brigade"... because they ignore FACTS to build completely false narratives to pull in people who believe what they write as Gospel truth when they've made it up out of whole cloth.
These people are not the "experts" they claim themselves to be. Jocko, you have to do what I do when presented with extraordinary claims: go back to the original source material and look for yourself. . . and then go to the manufacturer's specifications and check there. Then, if you don't know how to do the math, learn how and do it yourself.