I think it’s due to the mainstream idea of Jhanas and Samadhi as one pointed-ness. To me, Samdhi is a more broad category which is a state without 5 hindrances. When contemplating Anatma/Anicca etc mind will not necessarily settle on one object. But it will still be without the 5 hindrances.
From Saddhasutta
And how does a wild colt meditate?A wild colt, tied up by the feeding trough, meditates: ‘Fodder, fodder!’
i.e in-breath, out-breath, in-breath etc.
A fine thoroughbred, tied up by the feeding trough, doesn’t meditate: ‘Fodder, fodder!’ Why is that? Because it occurs to the fine thoroughbred tied up by the feeding trough: ‘What task will the horse trainer have me do today? How should I respond?’ .Tied up by the feeding trough they don’t meditate: ‘Fodder, fodder!’
Similarly meditate ‘What is the origin of this feeling/thought/sensation? What is the gratification?suffering? what is the cessation?’
In many places in pali canon, it is said that brahmas and devas come and say ‘noble person we don’t understand your basis of samadhi’.
Regarding joy, happiness in context to ‘Anicca/Anatma/Dukka/Asuba etc’, they do not lead to joy but perhaps to Equanimity. In any case these insight practices lead to disillusion and then lead to viraga.
disillusion → Viraga → freedom.
In comparison Joy,Happiness leads to Samadhi.
Joy/Happiness → Samadhi → clear seeing → dispassion → freedom.
Joy/Happiness path is more suitable for ‘Greed’ rooted people. Since Mediation gives them more Joy/deeper Joy they cling to the mediation deeply. After attaining Samdhi it leads them to see working of the mind and they grow dispassionate.
‘Anicca/Anatta/etc’ path is more suitable for ‘Moha/Avijaa’ rooted people. Their curiosity and the need to discern leads them to reason and disillusion with the reality. Growing disillusioned they grow dispassionate.