GAME BUILD 100.12.27812.0 (158884)
GAME PLATFORM: Steam
OPERATING SYSTEM: Windows 10
From Aoe Wikia:
Although the Gurkha is the counterpart of the Skirmisher for the Indians and was cited in the UI changes of the update 23511 that it is now tagged as Rifle Infantry, in reality it has not been tagged as Rifle Infantry, as it does not have the AbstractRifleman
tag in the game files. The same applies to its Mansabdar variant. This is probably due to a oversight of the developers.