That is pcie specification doesn’t always mean all hardware will have that.
From my understanding pcie arm is still evolving and does not have full speed. Last I remember pcie on rk3399 can only reach between 3-6gbp, cause the decent test on rk3566 shows that it maxed out at 3gbps which is basically 2lanes only.
There is a very strange question, does PCI-E in the kernel of nanopc-T4 work in Gen1 mode? But the SSD firmware engineer told me that my zhitai tiplus5000 got the rate of Gen2 after negotiation, but the PM981a seems to get the rate of Gen1 after negotiation, so what exactly happened on the nanopc-t4?