D&G talk about p.a. in Anti-Oedipus, in the chapter on capitalist representation. I’ll see if I can find the quote.

The prolongation of the working-day beyond the point at which the labourer would have produced just an equivalent for the value of his labour-power, and the appropriation of that surplus-labour by capital, this is production of absolute surplus-value. It forms the general groundwork of the capitalist system, and the starting-point for the production of relative surplus-value. The latter pre-supposes that the working-day is already divided into two parts, necessary labour, and surplus-labour. In order to prolong the surplus-labour, the necessary labour is shortened by methods whereby the equivalent for the wages is produced in less time. The production of absolute surplus-value turns exclusively upon the length of the working-day; the production of relative surplus-value, revolutionises out and out the technical processes of labour, and the composition of society. It therefore pre-supposes a specific mode, the capitalist mode of production, a mode which, along with its methods, means, and conditions, arises and develops itself spontaneously on the foundation afforded by the formal subjection of labour to capital. In the course of this development, the formal subjection is replaced by the real subjection of labour to capital.

[Is this where Negri gets his distinction between formal and real subsumption?]

And more:

From one standpoint, any distinction between absolute and relative surplus-value appears illusory. Relative surplus-value is absolute, since it compels the absolute prolongation of the working-day beyond the labour-time necessary to the existence of the labourer himself. Absolute surplus-value is relative, since it makes necessary such a development of the productiveness of labour, as will allow of the necessary labour-time being confined to a portion of the working-day. But if we keep in mind the behaviour of surplus-value, this appearance of identity vanishes. Once the capitalist mode of production is established and become general, the difference between absolute and relative surplus-value makes itself felt, whenever there is a question of raising the rate of surplus-value. Assuming that labour-power is paid for at its value, we are confronted by this alternative: given the productiveness of labour and its normal intensity, the rate of surplus-value can be raised only by the actual prolongation of the working-day; on the other hand, given the length of the working-day, that rise can be effected only by a change in the relative magnitudes of the components of the working-day, viz., necessary labour and surplus-labour; a change which, if the wages are not to fall below the value of labour-power, presupposes a change either in the productiveness or in the intensity of the labour.

Not stagist exactly, but he’s pretty clear than absolute comes first. Like you say about Tronti, I’m not sure of the importance here. It’s probably more than historical/factual, as Marx makes clear that their nonidentity is only known after the fact, “after the capitalist mode becomes general.” It seems to me that today it’s a political question: absolute and relative are capitalist strategies for extracting surplus value (and probably their only ones) and the proletariat needs to recognize those strategies in order to combat them.

But still, it seems a mistake to assume that these are finished processes, even the foundation of absolute surplus-value extraction, as Marx seems to hint at here. Could this be what Tronti is getting at? Absolute is not, as most Marxists have assumed, a frozen historical fact, but a continous social process? Just a guess. If I’m correct, this relates to D&G’s (and others following them) insistence that primitive accumulation is not a historical accomplishment but a continual goal.

Anyway, this is pretty jumbled and off the cuff. But your use of the word “moment” made me think this could be what Tronti is after.