Honestly if you want to freeze it properly you do it in an environment with no humidity, then would be no risk of condensation. It's a big risk without a zero humidity environment as anything on those platters could potentially cause irreversible damage.
Most people don't have zero-humidity environment in which to seal a HDD, so I'm not sure how the common person would achieve that. I won't say either way whether it is a substantial risk or not to actually attempt this -- I've no basis to make such a claim since I have no basis to know the likely hood of condensation forming on the platter in such a scenario. That's really the crux of the situation, unless we have evidence or someone who can comment on the likely hood, no-one can really say either way. I suppose you could say there is a large risk in doing something you aren't sure of and that's why I wouldn't try myself. It should be simple enough to show evidence, just repeating the procedure in the video above using a sealed HDD.
EDIT: Also, I'm still not even sure "how" this helps recover data. Does this help the drive spin up again or something? (In googling, I see claims of this supposedly stopping the head from grinding against the platter in broken HDDs, grain of salt though).