Currently get_ports is doesn't support the selection mechanism as all other introspection commands.
This is due to the fact that the select command doesn't distinguish bus indexes in the wire name.
The index part has to be extracted and removed when the selection is executed, but restored during the selection extraction.
Things to fix:

• get_ports port_name[index]
• get_ports port_name*
• get_ports port_name -filter {attr == value}