The effect of time dilation describes what happens when someone looks at a single moving clock. In your scenario, the train observer is looking at snap shots of multiple clocks. And by “look” I of course mean after accounting for travel time of light.
This is the next passage:Because your experiment as described does not show you time dilation. As @Pencilvester says, time dilation is an effect you get watching a single clock moving with respect to you (after correcting for the changing distance). You are looking at multiple clocks in sequence, thereby combining time dilation with the synchronisation of those clocks. That's fine as long as you are aware that is what you are doing, but it appears to me that your problem is that you think the combined effect is just time dilation alone. It is not.
Now it would appear this effect will persist even if you do not use different clocks each time as you can place A = B and follow any polygon or continuously curved line