Ok, my mind was blown today. On Ebay, on one of my regular leisurely trawls for interesting stuff, I found a Sawtooth Power Mac G4... only, it wasn't a Power Mac- it was a Power Macintosh!
The plot thickens. It's clearly a Sawtooth, with the Sawtooth-style power button and specs.
Therefore, I think we need to revise our assumptions. To me, it seems that the first batch of G4s, Yikes and Sawtooths, were both called "Power Macintosh". The serial number indicates this one is from week 46 of '99, i.e. November. Based on the specs (DVD-ram, no modem, zip, 450mhz), this was the most expensive G4 at the time- the other two models were a Yikes 350 and a Sawtooth 400 at that stage.
Apple's messy G4 run started with Yikes 400, ST 450 and ST 500, which immediately changed to Yikes 400, ST 400, ST 450 in late August with the speed 'dump' announcement; by October it changed to Yikes 350, ST 400 and ST 450, and in December, it changed to STs 350, 400 and 450; only finally getting the original 400, 450 and 500 models in Feb 2000.
Because they were only out for a mere 3 months, and they were only the higher-spec models, the earliest Sawtooths are actually quite rare.
I had a Sawtooth from Dec 1999, called a "Power Mac". So perhaps the Sawtooths prior to the December revision are called "Power Macintosh" after all.
More evidence will be needed. Still, this is really weird. Apple subtly renamed it's whole product line without any fanfare.
The more I research these early G4 towers, the more complicated it gets... I may have to make a table. The other thing I didn't mention was the corresponding availability of the original Cinema Display and DVI graphite Studio Display. The Cinema Display wasn't available until December 1999 (in limited quantities), and the Studio Display was also not available right on release. Very early G4 Sawtooths didn't even have a DVI port, making them physically incompatible with those digital displays anyway.
I wonder if anyone ordered a DVI Studio Display, only to discover that their G4 didn't have DVI...