To be fair, L&L sends out a diverse range of signals that could be interpreted in multiple ways. E.g. “pro” Dropbox:
“There are many cloud-sync services available but one that works well with Scrivener is Dropbox.” Source
in combination with “contra” Google Drive (in this case):
“Google Drive cannot be trusted with live Scrivener projects. While it is unlikely to be contributing to this specific issue, it is known to cause unrecoverable data loss in some situations. Please choose an alternative service.” Source
If I had to recommend one of the big players (Dropbox, Google Drive, iCloud, OneDrive), that is the least likely one to cause trouble with out of the box settings – which one might it be?