It was my belief some of the Macbook Pro's (1TB ? ) Pcie on the later ones had increased perfomance due to been 4 Channel vs usual 2 Channel.
Dont think there was ever a 4 channel 128GB though so you should be fine.. I'd not worry , and take delivery and test it..
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Quote from 9-5 Mac
"The MBP 15 is able to achieve these speeds because it has a 4-channel PCIe connection to the SSD, in contrast to the 2-channel link on the MBP 13 and MacBook Air models, though from some reader reports this may be the case only on models fitted with 1TB drives. PCIe is a high-speed serial link used only on the latest Macs, replacing the slower SATA connections of earlier machines. SATA 3 is good for around 600MB/sec, which was more than fast enough for hard drives but not capable of keeping up with the speeds of modern SSDs. PCIe 3.0 is capable of a theoretical maximum of 8GB/sec, allowing plenty of spare capacity for faster future generations of SSD.
Per lane (each direction):
v1.x: 250 MB/s (2.5 GT/s)
v2.x: 500 MB/s (5 GT/s)
v3.0: 985 MB/s (8 GT/s)
v4.0: 1969 MB/s (16 GT/s)
So, a 16-lane slot (each direction):
v1.x: 4 GB/s (40 GT/s)
v2.x: 8 GB/s (80 GT/s)
v3.0: 15.75 GB/s (128 GT/s)
v4.0: 31.51 GB/s (256 GT/s)
It seems likely that Apple was keeping things simple by citing the performance available across the range rather than noting the far higher speed of the top-of-the-range model."
I'm not sure if the SSD is different or just the "connection" to it .. Mac Pro's are also 4 channel I believe ..
