Need help with Carb Rebuild Question

[delta31]

While re assembling my carb, I noticed one of the kit parts was different that the original.
The step up piston and rod shown in TM 9-1826A (1952) Figure 83 shows the step up piston
having a small long diagonal hole thru it. The original part in the carb also had the hole but the replacement part
did not have a hole in it.

Do I have defective replacement part? Or was it found the hole is not needed?

I installed it as the rod was in better shape that the original.

Appreciate any advice with this.

Thanks