I recall reading/hearing that 10,000 or more G1 Units were pre-sold ... I bought mine on, I think, it was Oct 11 or 12. These 10,000 units were shipped with (in my case RC27) this build and the first OTA update Rc29 both had the ability to gain access to the root directory and Files...
I even made copies of all the apps I had prior to the hole being plugged.
So technically speaking the phone wasn't rooted in that rooted would imply that an action was taken to the phone to make it "rooted" and this is not the case ... No action was performed!! It just came this way..
For historical reference I had the linux commands to mount an Ext2 partition that first week of it's arrival, so the apps could be moved from the internal memory and stored on the sdcard ext2 partition.
So if your point is pure English symantics, then the phone was not rooted.
The phone arrived out of the box with root access by downloading a linux terminal app.