Looks like you’re referring Deployer 6.5.1, not 6.5.
I think you’re making assumptions about the capabilities of Deployer. The section you’ve quoted implies a capability of dealing with different source and target versions but I’m not sure that’s a safe assumption. Keep in mind that Deployer 6.5 can interact with older versions of wM components, but that doesn’t necessarily mean that it can deal with “upgrade” issues between different versions.
Given the error you received from Deployer, and the info about export/import having version limitations, I think it is clear that Deployer cannot use a deployment from one version to push to another version, at least when it comes to TN.
You may want to touch base with wM tech support to see if they may have info that can help you.