Re: Never attribute to malice that which is adequately explained by stupidity.
If what they need is xattrs then it sounds like there's an easy way out. They could, rather than saying that 'Dropbox will only work on filesystems x, y & z' say 'Dropbox needs xattrs to work. If the filesystem you are using it on has xattrs and supports them in a way compatible with ext4, then Dropbox should work. However we can't test all the Linux filesystems: the ones we test are x, y & z, so those are the only ones that we will support Dropbox on: if you have a problem with it running on some other filesystem then, at our option, we may choose to reject support requests'.
However one of x, y & z should be an encrypted filesystem, for sure.