A resource is able to view and select tasks completed before their start date (Hire Date).
For example, a resource has a Feb 28th hire date. It should not be able to select tasks for assignment to this resource who has finish dates that are before the hire date of the resource.
Release : 16.0.1
Component : Clarity Resource Management
This behaviour is working as designed.
The reasoning behind that is that it was allowed to be able to "pre-plan" with resources even if the date of hire has not yet arrived. Even if Default Allocation is 100%, it will not automatically give any allocation during that period.
In the Modern UX, it is possible to add the Date of Hire attribute as a column in the Staff section, so it might be desirable to have it visible if this is being used.