https://en.wikipedia.org/wiki/Nelson_Mandela_70th_Birthday_T...
According to this BB blog post[0] certain functions are unavailable ("making a new purchase, installing new trials, signing in to your account, creating new accounts, enabling B2, and creating a master Key"), and two B2 API calls (b2_create_bucket, b2_delete_bucket).
If these are the only disrupted features, then impact depends on the details of the use case (perhaps get object and friends have to be on demand but other changes can be async).
Now, why these specifics are in their blog post and not in the Scheduled Maintenance page itself, that is a fair question, because it leaves room for doubt that only this exact set of functions are affected each and every window.
[0] https://help.backblaze.com/hc/en-us/articles/227807447-Backb...
If it wasn't for the content and that they needed it ASAP I think regular air cargo would've sufficed.
They were out touring with an artist in some remote country, I think it was Kazakhstan, when the artists macbook suffered hard drive failure. Everything was backed up on backblaze, but the internet connections they had available was simply too unreliable to get the backup down. They contacted backblaze and for a price that was high (but not insane for a company) backblaze actually flew a guy with a physical hard drive to their location.
Saved ~5 gigs from being canceled, and my friend has been a die hard backblaze evangelist ever since.