You've asked a good question as to why that isn't a hudson...here's the reason:
Hudson's were developed in 1927 for both the NYC and the NYC&Stl (aka...the Nickel Plate Road). NYC 5200 was built by Alco Schenectaty while NKP 170 was built by Alco Brooks. The designs were based on impoving their respective pacifics, the K-5s and K-1s, by adding the 4 wheel trailing truck's developed by the Lima Locomotive Works and debuted with the A-1 which annihilated a mikado in a direct competition.
The engine in discussion here is a 4-6-0 with the tender attached to the engine frame making it more of a 4-6-0+4. It has a dinky firebox that rests in between the rear drivers. A Hudson has a massive firebox (supported by a four wheel trailing truck) that produces more steam than the engine can use. (hence the ability to sustain high speeds with a large train)
Prior to the advent of Superpower (a four (or six) wheel trailing truck supporting a large firebox), freight trains averaging 15mph were considered impressive. After the advent of berkshires, texases, and such, the speed improved dramatically. Once the four wheel trailing truck was married to 69"+ drivers...the Erie 70" drivered berks....the era of high speed freight was born.
The Hudsons allowed for improved fuel economy while pulling longer trains at sustained speeds (NYC K-5s were limited to 12 car trains...J-1s were a huge upgrade). Currently there are several surviving examples of these magnificent machines...(1) NKP, (5) CB&Q, (2) AT&SF, (2) CN, (5) CP, and (1) C&O. One of the AT&SF survivors is a super hudson. The most famous survivor is ex-CP 2860...the Royal Hudson...Good work to our friends north of the border for saving 7! The CN only had like 5 total!