The data for the page_views API is likely coming from Apache Cassandra, which makes it part of Canvas, and more reliable through the API. While the Requests Table is generated from logs, and data, and isn't fully accurate in the sense that things may be missed from time to time and collected/available later in the Historical Requests Dump from Canvas Data API. The Requests table also holds data for just about everything* that happens against your Canvas instance, while page_views are user specific.
This is a good read, Canvas Data Requests count vs. Canvas Analytics Page Views
Not sure if this is still true, API page_views call limited to a year
This might also be useful, Obtaining and using Access Report data for an entire course
*everything, The Problem with the Requests Table
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