Skirmish/GSA mode had the higher spare part limits for as long as I can remember. The D2 side was "fixed" to go past the stock 8 max limit. Unfortunately, the spares are not really doled out perfectly, and because ships in D2 don't pay a BPV cost in mission matching or award determination for the actual amount of supplies they carry, ships that would be much higher BPVs in GSA matches are treated like stock shiplist versions in D2.