System information (version)

• OpenCV => 4.2.0
• Operating System / Platform => Ubuntu 18.04
• Compiler => g++ 7.4

Detailed description

It appears that the pad value in darknet configuration files indicates the padding mode and not the padding value itself. I think pad being one implies same padding and pad being zero implies manual padding (which is specified in the padding parameter).

https://github.com/AlexeyAB/darknet/blob/dcfeea30f195e0ca1210d580cac8b91b6beaf3f7/src/parser.c#L180-L182

The OpenCV darknet parser treats the pad value as the actual padding value. There is also a comment which shows that the original author of the parser was stunned by the weird pad=1 and sets it to zero. It's actually zero because pad=1 would imply a padding of kernel_size//2 which would anyway give zero.