This is understandable, if a parent drops by too many times a day just because the parent is anxious, it is bad for everyone especially the children there.
And my heart goes out to good home day care providers who try to spin the day with so much in their agenda.
Sometimes when a baby cries during the initial settle-in times, it is hard for providers who have more than two babies. One starts crying and all the others follow. On top of it you have to clean, cook plan your schedules, activities...it is too much for one person to handle.
However, parent anxiety vanishes with trust and confidence.

All I am saying is one visit (or even different unannounced pickup times like how you suggest) is good enough to get an idea of how things are.

The harsh truth out there is there are some really bad providers who neglect and on the face might be very smooth with the parent. It really is a two-way thing. Either parties should win trust. Sometimes, having many babies ( especially a mix and match age group) is a very tricky business. The provider ideally wants all babies to follow a routine ( there is no other way when it is a one-man army) ..some are too young or not yet ready to fall into the routine.
I have seen disasters because of this. You do find some disturbing things when you drop in.
Experience is a must but ethics makes experience count.