Even if central contracts weren't a factor it is hard to imagine them not being in the squad now because they are either mainstays or too big a deal has been made of their inclusion. Maybe that is one of the reasons we are using so many forwards in the first place? He just doesn't want to make a difficult decision.
I agree, I would be a very difficult decision and the longer these forwards go without scoring in meaningful games the harder it will be for him to pair down and not just call up more forwards. Central contracts aren't necessarily a bad thing and can be beneficial but it does require a knowledgeable, ruthless person that hands them out and retracts them when necessary for the benefit of the squad and not on sentiment or seniority and I don't see that sort of person at the FA.
I think that Sampson has used Carney as an attacking midfielder more so than a classic forward so I don't know if she should necessarily be included. Also one has to factor in Sampson's penchant for "squad members" who are there for banter, cohesion and such and not for what they bring to the pitch, which I think fits several of the forwards mentioned.