guest systems are kind of complicated to poll. We can get all info for ESXs using VMware API but this is not the case for guest system. Guest system have to be monitored as standard node using SNMP to get all data because you need to monitor Operating system directly. If you have guest system added only as ICMP node, some info is not available. Try to set it up as SNMP and see if it helps.
Jiří, what you are saying makes sense, but some of the issues I pointed out seem to indicate that NPM does indeed already have the information. For instance, when we are looking at the ESX host, it has the names of the guests, but when drilling down into a guest, the name changes to an ip address and the managed by host shows blank. Also, the OS is listed on the overview, but not on the node details.
I'd rather not have SNMP running on every guest if I can avoid it.