Actually, Dino was - by the definition of a "marque" - a separate marque.
Moreover, Dino used a completely different chassis numbering system from Ferrari; Ferrari used odd numbers for road cars* and evens for race/competition cars sequentially beginning from 001/002, while Dino used exclusively five-digit even numbers sequentially beginning from 00102.
Later, and quite notably, when Ferrari adopted 17-digit VINs, a handful of the remaining holdout Dino-origin cars (the 308) had a Dino "ZDF" VIN even though the car had long since been rebranded to Ferrari - Dino ceased to exist in 1974, Ferrari adopted VINs in 1980*, the 308 itself was retired in 1980 - while all other Ferraris have a ZFF VIN.
The first three characters of a VIN are called the World Manufacturer Identifier (WMI), and comprises the country of origin and manufacturer. With "Z" being the prefix for Italian manufacturers (at least for ZA-ZU) I'll let you guess what the D and F mean in the manufacturer position. No I won't: it's "Dino" and "Ferrari".
As I noted above, the reason for Dino being a separate marque wasn't just the V6/V12 issue, but the fact his kid had the idea for the engine (for racing) and then died aged 24 of muscular dystrophy. Enzo wanted to honour Dino and named an entire marque and the engine that powered it (as he'd inspired it) after him. 60 years later we still have people denying it even existed.
Just to add to the amusement, FIAT bought half the road car concern from Ferrari a year previously, and it was FIAT that originally built the Ferrari-designed two-litre V6 engines - and the FIAT Dino coupe to house 500 of them to homologate the engine for the racing purposes Enzo wanted. Ferrari assembled the later 2.4 (after FIAT began production).
I could at this point show a picture of a Suzuki that's a Toyota underneath but which can be made by either Magyar Suzuki in Hungary or Toyota Motor Manufacturing UK in Burnaston and bear completely different VINs depending on which (TSM for Magyar Suzuki, SB1 fo Toyota UK). It's definitely a Suzuki, but also definitely just a Toyota with a Suzuki badge on it, and could actually be assembled by either brand.
However the point should be clear: who or where a car is from isn't quite as clear cut as all that in a surprisingly large number of cases, and you really need to know more about each individual case before declaring what something is and is not.
*Oddly, Ferrari adopted VINs some time around the serial number 30,000 and continued to use exclusively odd numbers for road cars until 75,000.