A visit that is limited to the lobby means that the supplier has not awarded the customer (or other stakeholder) representative the right of access. While concern exists over unrestricted access by customer reps to areas where competitor technologies might be displayed, the supplier that bars the customer from access to the lines where their product is being assembled, in practical terms, is failing to comply with the "right of access" requirement. That's why the verbiage in Revision C of AS9100 was improved to say:
7.4.2 Purchasing Information
Purchasing information shall describe the product to be purchased, including, where appropriate
My experiences have been that "where appropriate" is quoted as part of the same clause in not allowing visitors into certain areas (including auditors) - any one has access to their product in that area but not to the processes, equipment or sensitive areas.
These visits must be coordinated well in advanced and cleared before showing up at the facility - if not,you will not enter - as they claim - "where appropriate"
NOTE: Suppliers will let you know that security, proprietary, sensitive will superseded "right of Access".