Zuckerberg was recently in the press saying he wants Facebook to pay remote workers less (https://news.ycombinator.com/item?id=23264521). That could skew the results a little.
The prospect of a full time shift to remote was not communicated as context for the poll. Employees answered the polls thinking they were talking about how they'd go to the office given COVID-19 (a lot more people saying they'd do 50/50, when in reality, that just reflected their lack of comfort due to the disease).
Companies should be sure not to confuse actions people are willing to take due to a pandemic to be what they'd do in a post-pandemic world. Same thing with productivity: just like we don't know the long term impact of this disease, we also don't know that employees will remain as productive as they've been so far.
Too many people assume remote work always means working somewhere far away from a major urban city.