Are you saying that only a hotkey can page the actionbar, and not by calling it through the any lua code (during combat)?
Yes, in combat the action (paging the actionbar) must be initiated by the user, not the result of testing some variable in an addon.

For bartender to change the actionbar it must use the SecureActionButtonTemplate, which enforces the concept that the action must be tied to a user action. Secure templates allow addons to still have access to API functions that could be used for making bots but restricts them to being tied directly to user actions, which means bots cannot be written using the WoW API.

An example of an API function which is not protected is Follow. This is why you can make an addon to auto-follow after combat or to follow strobe. If Blizzard decided to protect this function in the API, the only way to follow would be as a result of a user action.