Question about Darknet53 and MobilenetV2?

[H-YunHui]

I have a question about the result of the red line in the figure below.

When using Darknet53 as the backbone network, the time required is 26ms, when using MobilenetV2 as the backbone network, the time required is 22ms.
MobilenetV2 is a lightweight network, has a much smaller amount of parameters and computational complexity than Darknet53. Why is the time required not much worse?

[clannadcl]

I also wonder about the reason for this problem.