I guess I never even felt heavy yet. I did get couched on KBR one time, maybe that is heavy, felt like I was being pulled inside my couch LOL. Pouni Ono puts me to sleep so maybe that is heavy. I have a pound of KWK Borongoru and that just mellows me out with no euphoria, doesn't really feel that much on my muscles or anything like that. Maybe I should try and find a straight heavy strain like you said and blend some heady in it.
I have heard heavy being referred to as being "couch locked", so yea I would say that is the same. There is a third discription "body", from what I get this refers to effects that help with tense muscles, pain, etc. If I am incorrect maybe some of the vets here can correct me, but this is what I understand them to be:
Heady: euphoric, anti-anxiety, peace of mind, social
Body: pain reliever, muscle relaxer, calm nerves
Heavy: relaxing, may help with sleep, case of the lazies