This blog post will be very short.
Few years ago I wrote the blog post about this topic. It is available here so read it for further details.
What we have today realized with my colleagues, this VMW_PSP_RR sub-policy options is enabled by default, therefore VMware Round Robin multi-pathing policy is considering I/O latency for optimal storage path selection.
The ESXi setting can be validated in ESXi shell by command
esxcfg-advcfg -g /Misc/EnablePSPLatencyPolicy
where the output in ESXi 6.7 U3 and above is
Value of EnablePSPLatencyPolicy is 1
Note: 1 is TRUE.
This is the reason, why you can observe different traffic via different storage paths.