Yes, that's fine and as per the design. If you look at the pinout diagram in the thermocouple amp section you will see that only 4 pins in that IC actually do anything.
I have built 2 HM's using Peters boards without issue.
I have 4 HM4.2.4 boards left from my latest batch.
The price is still €8 for a single board. I might also be able to print cases and I have enough RPI connectors and probe jacks left to help a few forum members out (saves the shipping cost of the Digikey parts).