Stiffness and friction have a significant effect on the outcome of the analysis results. Ideal anchors have infinite stiffnesses , but real anchors have different behavior. We might have used ideal anchors with infinite stiffnesses in analysis , which will yield higher stresses and forces , but might be in practical anchors dont have that must stiffness that we have used in our analysis .

So, we should try to simulate as close as possible the real world environment , although I agree that its difficult to get exact stiffnesses values of the real world supports , but we should try to evaluate it with good Engineering judgement.