tryed 15.0.0, 15.0.1 and 15.0.2, upgraded (also uninstalled and reinstalled) tools: the Windows XP Pro guest NEVER go in Unity mode.
reinstalled Workstation 14 and Unity worked at first click!
In the logs I noted that WS 15 wrote that exists a newer Tools version but this is false.
At least I am not going insane! 10.0.12 is the latest version of tools for Windows XP, but with VMware 15 it seems to think it should erroneously have a newer version. Here is what my log was also saying:
2019-05-02T14:14:05.255-04:00| vmx| I125: ToolsISO: Updated cached value for imageName to 'winPreVista.iso'.
2019-05-02T14:14:05.255-04:00| vmx| I125: ToolsISO: Selected Tools ISO 'winPreVista.iso' for 'winxppro' guest.
2019-05-02T14:14:05.255-04:00| vmx| I125: TOOLS updated cached value for isoImageExists to 1.
2019-05-02T14:14:05.256-04:00| vmx| I125: VMXVmdb_SetToolsVersionStatus: status value set to 'ok', 'current', install possible
2019-05-02T14:14:05.256-04:00| vmx| I125: TOOLS installed legacy version 10252, available legacy version 10338
I am not sure what legacy version 10338 is and I am not sure if there is a way to trick it in the meantime until VMware finally fixes this issue. I really need this fixed ASAP!
Quick update, I noticed there was a VMWare update today to v15.1. I installed it and tried reinstalling vmware tools on the XP VM as well after this with no luck. The issue still exists.
I also tried changing the hardware compatibility back to version 14.x for this VM without success either. The issue appears to completely be with Workstation v15.x in general and it would be great if they could fix it with an update to the vmware tools or application itself.