Using the rasterized fonts is very much an edge case these days. I'd also note that back when I used to manage this on University systems (in the days before dvips would automatically call mf to generate needed fonts), it was often the case that at lower resolutions (<600dpi), the CM code often ran into errors from the necessary mode_def parameters. Xerox printers were especially troublesome because they used a "write white" strategy for printing. A "write black" printer (e.g., the classic HP LaserJet), marked the page by using a laser to charge the parts of the page that should get toner. A "write white" printer charged the whole page, then used the laser to remove the charge from the parts of the page that should not get toner. On a "write black" printer, a pixel was a little bit bigger than its claimed size. On a "write white" printer", a pixel was a little bit smaller than its claimed size.

I was supporting Xerox 8700 laser printers at the time and the settings for a write white printer inevitably caused errors for many characters until I was generating at least a .600gf file. I have vague recollections of the same issue coming up occasionally even when I was printing to a 1200dpi Compaq.