53.0.2785.116 is the version showing with Get Info. It probably upgraded itself the same day I posted last week. I assume the 53.0.2785.116 directory is the 'saved' version of the current app. The app and that directory have a distinctly similar name.
The only thing in there is a .framework collection of files totally 204.5 MB. The current app is 402.1 MB.
The only other version is the 52.0.2743.116 directory of 197 MB. Didn't bother keeping the o;d version, so I don't know its size (I'm too lazy to reinstall it from TM or CCC!).
In my case, anyway, while Chrome is not completely deleting its old files, it seems to be cutting its space usage by about 50%. I suppose my neglecting the app allows me to
not waste much space?!
Anyway, thanks for the tip, I now have ~197 more MB of disk space.