What facts (legit 3rd party rumours) are you referencing to assert that it is less likely?
And no, the fact pattern does not support a keep one trade one strategy: They increased their offer to Horvat in January after having signed Miller in the summer.
I took your statement that your argument isn't with my conclusion as seeing it as a viable deduction. You've admitted that here by stating that it's one of the few possibilities. Where have I put words in your mouth? (Not my intention at all)
If I'm correct, you are saying "this is what happened" and I'm saying "it's one of the possibilities". Those are different conclusions.
The reports on the negotiations, including the reported last offer, to me describe a team that would keep the player for a certain bargain amount or trade him if they couldn't get him signed. But again we don't know some details that are really, really, important. For example, do we know if the first/low ball offer carried a full NMC? Do we know whether or not that last offer had full trade flexibility for the club? To my knowledge there are no reports with that level of detail. If they up their offer but removed the NMC, that would be a massive change in value for the club. If they didn't want to keep both Miller and Horvat long term, they could sign both with one having trade flexibility for the club. This could also be a reason for the Horvat camp not to accept the offer knowing he could be traded at any point. Clearly, this is just pure speculation but speculation because
we don't have the details. It makes a huge difference. And even then, we are not in the heads of management. We can only go by what tangibly happened (Miller was signed and Horvat was traded). To me, the most logical conclusion is that the club felt they had two options: 1. sign both if they could get a bargain, or 2. sign one and trade the other from a position of strength, knowing that they would retain two high end centres, to fill a position of weakness (RHD).