Reading on about this it said the best meat to use for Bistecca fiorentecca comes from the Chianina breed of cattle, I checked on this and here what it says lol

The Chianina (Italian pronunciation: [kjaˈniːna]) is an Italianbreed of cattle, formerly principally a draught breed, now raised mainly for beef. It is the largest and one of the oldest cattle breeds in the world.

 The famous bistecca alla fiorentina is produced from its meat.

One of the oldest breeds of cattle, the Chianina originates in the area of the Valdichiana, from which it takes its name, and the middle Tiber valley.^[3] Chianina cattle have been raised in the Italian regions of Tuscany, Umbria and Lazio for at least 2200 years.^[4]Columella, writing about types of oxen in about 55 AD, says "Umbria vastos et albos ..." (VI.I.2),^[5] which in the first English translation is "Umbria has such as are huge, and of a white colour".^[6] Chianina oxen were the principal source of agricultural power in the area until displaced by mechanisation and the collapse of the mezzadria system following the Second World War; they were in use in agriculture until at least 1970^[7] and are still used in processions such as the corteo storico of the Palio di Siena. From 1931 breeders began to favour selection of animals more suited to meat production, with shorter limbs, longer bodies and more heavily muscled rump and thighs; recently, selection is based also on factors such as growth rate, meat yield and, in cows, maternal ability.^[4] While one source reports a Herd Book dating from 1856,^[8] others date the institution of the Libro Genealogico (genealogical stud book) to 1933, when a breed standard was established and commissions were set up by the Ministero di Agricoltura e Foreste (ministry of agriculture and forestry) to identify, mark and register morphologically suitable animals; the standard of the Chianina breed was fixed by Ministerial Decree of 7 August 1935.^[9] A private register was previously kept by the largest cattle breeder of the Sienese Valdichiana, the Eredi del conte Bastogi of Abbadia di Montepulciano,^[9] and a group of breeders had in 1899 formed a society, the Società degli Agricoltori della Valdichiana (society of farmers of the Valdichiana), of which a principal aim was the establishment of a herd book.^[10][11] Since the Second World War the Chianina has become a world breed, raised almost exclusively for its high quality meat, and has through exportation of breeding stock, of frozen semen and of embryos, reached China, Russia, Asian countries and the Americas.^[

Meat production

In beef production, Chianina cattle are chosen for their growth rate, which may exceed 2 kg (4.4 lb) per day,^[1] the high yield and high quality of the meat, and their tolerance of heat and sunlight. They are good foragers and are resistant to disease and insects to a greater degree than many other domesticated cattle. Thanks to these qualities the Chianina breed is present in many countries such as Brazil, where there are many thousands.

The ideal slaughter weight is 650–700 kg (1400–1500 lb), reached at 16–18 months, where the yield may be 64–65%. The meat is renowned for its quality and nutritional values.^[1] In Italy it is sold by name at premium prices by approved butchers, the sales receipt detailing the breed, birth and slaughter dates, identification number and other data of the animal in order to guarantee its origin.^[19] Each of the 18 principal cuts is branded with the "5R" symbol of the Consorzio Produttori Carne Bovina Pregiata delle Razze Italiane (consortium of producers of quality beef from Italian breeds), signifying the five indigenous beef breeds of Italy, the Chianina, the Marchigiana, the Maremmana, the Romagnola and the Podolica, in accordance with a ministerial decree of 5 July 1984. For the three breeds present in central Italy, the Chianina, Marchigiana and Romagnola, there is also an Indicazione Geographica Protetta, or certification of region of origin, in accordance with European Community regulation 2081/92.

^[15]

Just thinking outside the box here maybe they mean, not a first cut p.h. but one cut from where the tenderloin tapers down, more of a center cut? Anybody who knows anything about meat knows the p.h. end is the larger end.