Slowakische Kassettensite mit allen Einlegern

[2245]

UX-pro was once speculated to be Metal Type II

I'm pretty sure that this is not true.

Magnetite... Taiyo Yuden, who explained it in their 1985 catalog.

Magnetite is only mentioned as pre stage material in the That's brochure. This is nothing special for Type I or Type II, because it is the usual pre step before getting the γ-Fe2O3.
Unusual is most probably the inhouse use (reduction) of magnetite to get their Iron particles for Type IV. Most makers were just buying the Iron particles.

TDK is inaccurate and misleading in their infromation

Because of?  They were giving more information to consumer customers than many other makers. And their numbers are quite accurate.

I learned that for Suono cartridges they use a material they call composite resin

Composite resin is a very common term for mixed materials. As far I know the Suono composite is made of Polystyrol, somekind of rubber and metal powder.