The download will be fine.
My concern is over the time being taken when the disk is nearly full.
I assume that it is either performing some major reindexing or is changing the file system type and having to go through a major rewrite of data.
Anything like that sounds risky to me.
The release notes that I linked to also says:
Transitioned to a more flexible and efficient way of organizing content on device storage
I do know what firmware is.
In my first post in this thread I included a link to the changelogs for this firmware update and selected some very specific text from it … and my question is about that text.