Almost certainly flatly untrue. Medical debt in the US goes to collections agencies all of the time. According to the CFPB, consumer credit debt from credit records totals around $88B USD. If this was some sly loophole, someone would have figured it out and won in court by now.
This seems like bad advice at best and actively harmful at worst.
I have the same issues with Nextcloud as OP, regardless of the hardware it's running on or what kind of optimizations I've done, but I've always hesitated to use Seafile because it doesn't keep the files in tact. They are chunked/encrypted or something else, which I'm sure helps performance, but I really value having my files just be regular files with Nextcloud, so if I ever want to take them out of Nextcloud without the help of the application, I can just do that.
I wish Seafile had an option to maintain the file integrity. If it did, I would definitely give it another try.