You are absolutely right. I've mentioned it before.
There are about 750 bugreports filed against subiquity since it was introduced 18 months ago. 
The installer is a flutter app in a snap running parallell to a diskchecker. It is sheer madness. Why would they jail the installer ? for what ? 
Really I would rather have a good working classic textmode installer than this piece of unreliability. I've thought several times to switch to kubuntu in the future just because of this.