You can be sure its two performance cores. Apple needs the efficiency cores to maintain the battery life they are promising.For $2000 starting price, I was expecting a non-gimped CPU. Kinda greedy on their part honestly.
Especially if 2 of the big cores are disabled, that would be a 6 + 2 CPU, significantly less power than an 8 + 2.
They want an additional $300 to get to the real spec of 10 core CPU and 16 core GPU. Ridiculous.