Having the GA tracking code on both pages eliminates the need for hitCallbacks. Instead, simply assign different events to each link from page A to page B.
From my own experience, hitCallback proves most valuable for tracking outbound links - particularly when a user clicks a link that takes them away from your site. In these cases, the new page may load before the GA script has had a chance to register the event. HitCallback solves this issue by ensuring the event is captured before the new page loads.
However, when a user navigates from one page to another within your own domain, GA will capture the event while the user is on Page B (if it wasn't captured on Page A). The event is placed in a queue by GA before transitioning from A to B. Once Page B is fully loaded, the GA script processes the queue and sends the event data to Google. This process is characteristic of GA's asynchronous nature, which was implemented in 2009. For a detailed explanation, check out this article from that time.
The reason hitCallback isn't effective for outbound links is that when a user's browser leaves your domain, the information stored in the browser's Javascript global variables is lost - including any events in the GA queue that haven't been sent to Google. For these scenarios, hitCallback can be utilized to ensure event data is transmitted before leaving your domain.