How likely is it that the quick increase in network hash rate is related to the ASIC manufacturers getting their new hardware online while they mine before they send the hardware out?
Not likely at all. We currently seem to be well above 18PH, compared to 12PH in the beginning of the month. Lets assume its HF that is doing the hashing. 6PH = 6000 TH = ~15000 baby jets. Imagine what it takes to "temporarily" mine with 15000 of those machines drawing a total of 6 million watt?
Even if these vendors were self mining with their sold hardware, it would barely register on the network. Hashfast first batch is what, 500 babyjets? Thats 200TH. Statistical noise.