I have a 7-month-old, too ... and this would REALLY bother me. I think you have every right to question this and I would talk to them about your concerns. My daughter just now got better at taking "regular" naps, but I still let her dictate her schedule a bit (although she's worked into a pretty regular routine on her own). I don't think letting a baby cry (especially that long) is okay ... and you're paying them to take care of her.
My son was in daycare until 13 months old (since then I've been a full-time stay-at-home Mom). He was a TERRIBLE napper at daycare. He was far too distracted there to sleep, and that would interfere with him sleeping well at night (because he was too tired). I think any caregiver should work with the parents to provide the type of care that works best for ALL (not just them). Best of luck to you with this!