They continue to obfuscate the details of the neck joint on the website, GaH. I don't know why they're doing this. They've been clear about the finishes they've been using, but they don't seem to want clarity with the joint... In the description of the D-55, they mention the dovetail joint, but unless I missed something not in the description of the F-55 (or 12-string versions). I can't assume one way or the other, but I guess those have dovetails too. I don't see much about "Traditional" here on the site either, so I can't make that distinction for you.
Anyway, good luck. We have discussed this before, as you suggested, but it's an annoying topic as mostly what we have is hearsay (as I recall). I'm pretty sure the neck joints of the first guitars (M-20, D-20) were mortise and tenon joints, but I'm not sure about any of that.