Wait Stats on Microsoft Azure test
In SQL Server a Latch used to provide brief, exclusive access to a database page.  When multiple sessions need to modify the same page, all but one will enter a "PAGE LATCH (non-I/O) wait".  Your wait stats seem to indicate that all your sessions are lining up to modify a single page.

There are couple of different scenarios where Latch contention can become an issue.  The most common are when all a large number of sessions need to write to the same "hot" page, typically at the end of a clustered index, and latch contention in Tempdb for metadata pages when a large number of sessions create and drop temp tables or table variables.  See  Diagnosing and Resolving Latch Contention on SQL Server for details.

But in the context of a synthetic load test, this Latch contention may represent a defect in the test workload design that is preventing the sessions from running concurrently and accessing all of the server resources.