LrC not recognizing newly updated ratings from Bridge

One cautionary point: by default with Lightroom Classic, develop edits plus any and all organisational metadata worked on in the Catalog, are stored in the Catalog only. In that case the external file's metadata  will not include any record of this work done within the Catalog environment.

"Read metadata from file" creates a new History state wherein not only are e.g. ratings introduced that were applied externally, but also wherein the whole image is reset back to whatever that external metadata holds for its Develop appearance, keywords, etc.

So if that other stuff has not been previously written out (up to date) before reading it all back in again, you will see more change in the image than you bargained for. That change (resetting to an unedited appearance for example) is still reversible by rolling back the Catalog's History to its state just prior to the "read".  But that would need to be done for each affected image.

If you had previously written everything out up to date, or else had LrC automatically write that out continually as it went along, then this method can work. However I would agree that rating etc within the Catalog or else within Creative Cloud in a manner that syncs in a Lightroom aware manner to the Catalog, is far the more elegant and robust way.

Mingling Catalog-centric and file-centric methods together, is IMO simply doomed to frustrate because it clashes paradigms. For example: how could one use Bridge to apply ratings to virtual copies?