Hey @GabrielPaganAbarcan,
This behavior of free space being slowly presented back to the cluster is expected behavior for Nutanix.
The reason for this is because of the service responsible for cleaning up space, Curator. The curator takes time to perform scans on the cluster to reclaim space.
To know in detail about the Query, please take a look at KB-2924
Hope this helps you.
Regards,
Shaurya Bhardwaj