Why use multiple regulators?
The LT3080 as used in the design you've linked to is rated at 1.1 A, as the design is showing, it is supplying 1.5 V at 2.2 A max.
The speed of a smaller LDO is often higher than a larger LDO so the accuracy is higher, not sure on this but the availability could be an option, if you look for an 3 A 1.5 V LDO on Farnell, there is no SMD component available, only 1.5 A variants. However, most of the times in the design I work with, it has to do with heat dissipation and spreading. Not one hotspot but two less-heated spots are beneficial to the construction of the housing.
Refer to page 11 of the LT3080 Datasheet.