Tenuous atmosphere planets could be blocked just as they all were for Dangerous users v Horizons.
They could, but I see that as less likely.
The whole "new planetary tech" and granting of the ability to cross the exclusion zone of Horizons made that a much easier demarcation to make.
With Odyssey I'm not so sure, because the updated surfaces will be rolled out across the board* and it seems like there'd be a good bit more mingling. It'd be simpler to allow it, and just keep you stuck in the chair. But I may be wrong, it could be done via a new 'planetary approach module' and otherwise kept as-is, with anything marked as 'atmosphere' being off-limits.
I still think that's unlikely though, given that
functionally speaking 'tenuous atmosphere' planets are airless worlds with a prettier sky, but otherwise no different than what we have now. The VR/non-VR divide also plays into this, because it really feels like from a technical standpoint Odyssey isn't so much an expansion as it is an entirely different sub-game that uses Elite as a front end.
I'm deeply speculating at this point, but in my view a whole bunch of circumstantial evidence points toward everything but 'flatscreen', on-foot content getting rolled into the core of Elite.
* I suspect this is ultimately what drove them to roll Horizons into the base game - it became too difficult to integrate up to 3 versions of any given planet, so they flattened the products into one, and will roll out those changes to a unified base.