Venerable Maggavihari says something like the below in one of his Sinhala video lectures:
Alobha is not the absence of Lobha. It has a different function. Lobha is craving/attaching/holding and the Alobha is anti-craving/detaching/unholding. Likewise Adosa and Amoha.
These six cetasicas are called hetuppaccaya (root causes) in Abhidhamma. Roots means the cetasikas that support other Nama-dhammas to establish on the object well by taking the object hard.
Therefore the alobha, adosa and amoha also have to be functions that take the object hard. They are not the mere absence of Lobha-dosa-moha.
What do you think?