IF it has same physical size, same voltages, but claims twice the current it simply is not true.
SS electronics advances day by day, tubes are basically same as 50/60 years ago, average silicon steel same as 120 years ago, no new revolutionary advances allowing the doubling of performance for same weight of steel.
Even less performance change for same weight of copper.
Design equations, graphs and tables from 1947 Radiotronīs Designer are perfectly valid today.
If anything, itīs hard to get steel as good as old Armscor and similar, not because "we know less", far from that, but because we donīt want to pay for it, go figure.
Consider that same size same weight iron and copper standard Marshall transformer as a same specs clone, not a miraculously doubled performance improvement.
Now if it were an SMPS, yes, modern Ferrites can reach even a MHZ, some even more, garden variety types are comfortable with a couple hundred kHz, while 1947 flyback cores "just" could be used at 17kHz so there a modern core can easilyprovide 10X the old performance, but .... on laminated silicon steel? ... forget it.