Hello, the issue is still present at version 5.0, from the release notes
https://www.vmware.com/support/vsphere5/doc/vsphere-esx-vcenter-server-50-release-notes.html
The exported list of virtual machines might be incomplete
When you select a datacenter, cluster, host, or other object in the vSphere Client inventory and export a list of its virtual machines, the list might not include all the virtual machines. This occurs because information in the list is not always populated for objects that are not visible.
Workaround: Before exporting, scroll through the list to make sure that all virtual machines are displayed.
I hope it helps
Regards
Simone