Freshness of prawn

This is one confusing matter. Some say the fresher the prawns, the easier it is to peel the shell off the flesh. My mom disagree and said that the harder to peel, the fresher the prawns.

Looking to googles for answer.
-Some say that the difficulty of the peeling may lies with how well the prawn is cook.
-Others stated that this may be due to how stressful the prawn is before it breathe its last.

It does seems like there is no concrete evidence to link the freshness to the difficulty of the peeling.

All I know is, from my experience of keeping prawns, the harder to peel the shell, might be linked to how recent it shed its outer shell.

Any chef out there that can help?