I know a few people who actually became advisors as well. But they had little previous success (or none) and I've always wondered why would any founder take advice from someone who's not done it before and succeeded. The fact that OnDeck hires these people as advisors is a turn off.
Furthermore, like you said, their experience can be replicated and I highly doubt the quality of the network they have.
Also, the problem with this program is that they get their results upfront (the money you pay to join) and really have no problem if you completely waste your time there and do nothing at all. Whereas an accelerator (YC for example) ties their success to your success, in fact, they're willing to give money to bind their own success with yours (which is why they end up having the highest number of exits and IPOs out of any accelerator in the world).
Finally, even in your post here, notice how there's no clean "it's totally worth it" statement here. This seems to be a recurring theme in my research.
They probably are very well-intentioned, it's just that, in my opinion, despite the good intentions, it's not a great program even for first time founders. Hungry founders will always find the way to the needed knowledge and network, especially with today's available tools and online communities etc.