VDIs are allocated during the provisioning stage

Why is a VDI in a VDI Pool allocated to a user using the Virtual Desktop even though the VDI is in “provisioning status”?
If VDI is allocated to a user in provisioning state, and the user tried to use the Virtual Desktop fails during provisioning, (due to an issue with provisioning, or post provisioning of the VDI, or the connectivity to SCVMM breaks etc), then the user would just see that the VDI is in “provisioning” status. And if the provisioning fails the cleanup job will remove the VDI.
So I wished to understand why it is configured in this way? is theres a specific reason? Why not just wait for the provisioning to finish before the VDI is made available to the user?

A user is allocated a system to queue the provisioning state. Otherwise a system coming online could be deemed idle and pruned due to the constraints set on a pool.

Other VDI platforms allocate a spinning up resource. The key is you highlighted if the provisioning fails we terminate if the instance. Are you saying that we then don’t trigger another rebuild for the user?