Perhaps one should encrypt files before uploading to cloud services. Sure it destroys the possibility of webview for your data, but then you don't have to worry about situations like this.
Unless they decide that encrypted files violate their TOS.
Which should be a red flag not to use the service because they're collecting your data for any and all reasons.
This is your redflag
That's what steganography is for.
I've been using rclone+restic to back up files to my university-provided Google Drive, which has unlimited storage. Apart from occasional "rate limit exceeded API warnings", I haven't faced any issues so far. Wonder if that'll change with the new policy.