Something tells me the mom doesn't want one big afternoon nap because it prevent the kid from falling asleep at 5pm. I would think that sleeping 2 hrs, likely from 1-3pm makes the kid resist such an early bedtime. Whereas a short 30min nap at 1pm likely has the kid exhausted by 5pm.

I have it in my contract they must sleep/rest for 2hrs after lunch. None of my families have an issue with it but should they start to I can point to the contract. Some of mine still do 2 naps (12month olds) so I don't enforce the full 2hrs if they did a good morning nap.