Generally true, however last year Tivo allowed you to do just that in some cases, and with a fee. I transferred a lifetime sub from an older series 3 to a roamio ota for $99.TiVo lifetime subscriptions are attached to the DVR itself, not the owner.
For the purpose of the thread though, this is not something I would count on them doing again.
Edit: it seems it was two years ago when I did this, however they did offer the deal again last year to transfer to a Bolt.