@paulbnp Thanks for reaching out!
I took a look at the pants you are asking about and, if I am understanding your question correctly, that is the design of the pant. I have a couple of pairs of lightweight, breathable pants and they are designed similarly. They all have rear pockets that have mesh against the wearer and then the outer pocket. I believe this is done with intention of providing some ventilation and also preventing discomfort of too much material when the wearer is sitting down.
If your husband is looking for a place for his phone, I would recommend the zippered thigh pocket as that provides a measure of extra security.
I hope this helps, thank you!