Hydraulics were an option on the G,I've been around Allis tractors and the G most of my life. I've only seen 4 with loaders, the one in your picture belongs to a good friend of mine who lives just up the road. As you can see, it's a very small bucket with a hand dump latch assembly. Yes it is a load on the front end and does tax the steering to the max. In it's day I'm sure it was a good cheap addition to a small farm and beat a shovel loading a wagon. The loaders were not made by Allis, but were produced by the Midwest Co.
Here is the brochure and also a picture of the shortened version