Does the Absence of Marcion, Basilides and Valentinus from Justin's Syntagma Mean that He Did Not Think They Were Heretics?

We have been following the underlying shared narrative beneath both Irenaeus's Against Heresies and the Philosophumena (a text generally thought to be written by his student Hippolytus but which is attributed in the MS to Origen).  In spite of the fact that both texts have been expanded in different directions, there is a common order to both:

1. Simon and Helen (AH 1.23.2b - 4;Phil. 6.14, 15) 
2. Saturninus/Saturnilus (AH 1.24; Phil. 7.16) 
3. Carpocrates (AH 1.25; Phil 7.20) 
4. Cerinthus (AH 1.26.1; Phil. 7.21) 
5. Ebionites (AH 1.26.2; Phil. 7.22) 
6. Nicolatians (AH 1.26.3; Phil. 7.24) 
7. Cerdo(n) (AH 1.27.1; Phil. 7.25) 
8. various (e)ncratites (AH 1.28; Phil 8.9,13)

It is not impossible of course that either Against Heresies or the Philosophumena 'retains' some of the original order of the lost original ancestor text which was not followed by the other.  Nevertheless it is very interesting to look at this list and notice what is missing - Marcion, Basilides and Valentinus.

Given the fact that Justin is usually thought to be the author of the lost syntagma behind these catalogs and given that that Justin has kind things to say about at least one of these men (Valentinus) and Vinzent has shown Justin borrowed, used or used a text with readings in agreement with Marcion's gospel, the fact that Basilides, Marcion and Valentinus do not seem to have been a part of Justin's original text is quite intriguing.  It is also tempting to see the list as chronological in nature, making Cerdo or Cerdon the most recent 'heretic.'