I understand your point but since you want to use automatic autotooltoifying and since you need to explicitly set AutoToolTipify the expect result is automatic tooltipifying and not nothing to happen. That is why the developer should handle the case of zones and their IDs, furthermore there are other ways provided to tooltipify exactly what you need. This being said, the automatic tooltipifying is used only for simple base scenarios and for fine-tuning dynamically adding of target controls should be used.
For your particular case I suggest to simply put an empty DIV element with the ToolTipZoneID on the content pages which do not have such - in this manner you will trick the tooltip manager to tooltipify only it and since it is empty noting will get tooltipified on this page.
On a side note, in order to get a faster and ensured response I recommend to take advantage of our support system and to open support tickets which are handled with a high priority while the forums are considered community resources.
the Telerik team