(More than you ever wanted to know...)
The prog board is 4-layer, and the internal planes act as a bypass capacitor as well, so you may as well get away without. As the guy says it depends on many factors like power supply quality or board layout.
My current version of the prog board is 4 layers, just because I don't have the equipment (or experience) to properly test this. The CPU runs at 20Mhz, which is far outside the range I normally do as well.
So if you have them laying around you can put them on. But if the board works stable for you you can leave them out as well.
The post was edited 1 time, last by Fluffy ().