Let me try differently: They are already in the falloff when you start! Go from Y+ to Y-. Hence why they are up above the letters already.
Please have a look:
Compare the color (white/blue), then switch the Plain Effector on and off.
When this file is clear, check out this file:
The original position is on the letters, and so is their starting point. When you move the Falloff up: You move them out of it. I have set the Linear-Falloff to 1cm to make that more clear.
The initial point is the point where the linear Field is working on. If this moved with the current field they perhaps would move out of the Field. Being out of the field would mean, that they go back to the letters. But then they would be in the Field again. This would not work at all. Based on that, the points of the “particles” stay where the Field started to work on them.
If a new Field would add to that (perhaps the Clamp option is off), the new Field that is processed after the initial one, will work on where the clones are then, based on the work of the first Field. To illustrate this, switch on the Spherical-Field, to see the effect.
Your scene works just as expected.
Please let me know if that makes sense.
My best wishes