That isn't what he claimed. He simply said it was molten.
Molten doesn't equal liquid. Laymen will often use a term such as molten when what the really mean is the material is glowing red/yellow/white hot. This is why us metallurgists refer to a liquidus when referring to metals or alloys and their melting points or ranges . I'd never describe a metal as molten, because it doesn't convey any definitive meaning.
For example a layman might think that a steel member is melting when it's only another metal or alloy, such as aluminium (MP @ 660°c) or lead (MP @ 327°C) or tin (MP @ 231°C) or copper (MP @1083°C) that have far lower melting points than iron (MP @ 1538°C) or plain carbon steel (as low as 1425°C), running down a red hot iron "beam".
If a metal is fully liquid it has no crystal structure and therefore cannot remain as a shape. The liquid will take the form of whatever it flows into. Therefore someone seeing liquid will not describe that liquid as a solid shape like a beam. If there were accounts of large amounts of liquid metal at ground zero then there would be evidence of this because it would be extremely difficult to remove and would subsequently show up when examined by the teams at fresh kills, just like the steel that was severely corroded due to high temperature corrosion in the rubble pile.
It is also difficult to pick liquids up (referring to the grapple photo) especially those whose temperature is greater than 1538°C. Most people have no idea how hot that really is nor how corrosive iron is at that temperature. Refractory lining in steel making has to be replaced as a part of ongoing maintenance due to the corrosive nature of iron at this temperature. A diggers bucket or grapple isn't going to last very long in that environment and the rest of the materials such as gaskets, hydraulics, seals and oil are going to last a lot less - I'm talking minutes.
Liquid iron is extremely dangerous, there's no way people would be risking their lives or machines trying to remove such material.
I've had furnaces running at 1000-1100°C for heat treatment of steel and it's quite amusing to see some peoples' reactions to the inside of the furnace especially when you tell them what temp it's at then ask them to move back a bit, then take a sample out and plunge it into quenching oil!
Similarly
metal does not equal steel: it is impossible to tell what a material is just by looking at it. I can't do it and no-one I know can. You have to rely on external clues to try and deduce what the material is. So it's even possible for someone to describe what they think or have been told is a steel (iron) "beam" melting when actually what they are seeing is aluminium cladding or some other alloy melting. It's not uncommon to get metals or alloys in a fully liquid state in fires because there are plenty of alloys and metals that have melting points below the temperatures fires can produce- see above.
Now I know you may feel the need to post pictures showing the colour of liquid aluminium as being silver, but we've been through that a thousand times on this forum so please don't.
I hope this helps to clear that part up.