It is the grip directly beneath the gimbal, but it is not soft foam. It is textured hard metal. Some operators put bicycle grip tape or the like on it, but in order to be responsive it can't be squishy-soft.
The Glidecam post is both small and slippery. If you are very clever and have access to some machine-shop tools you could fashion an add-on grip. Practically speaking, the best you may be able to do is experiment with tape to increase the friction so you can improve control.
There are some brief explanations of grip, technique and related topics in the various Steadicam manuals that Tiffen has on the Steadicam website. Start with the Pilot and Scout manuals.
By the way, when I say "serious about the craft" I mean "serious about improving your work". It's not about your gear (except to the extent that your gear will limit you as you get better) or your ultimate career path. It's about caring about doing your best right now with what you have right now.
And you should invest in the Steadicam Operators Manual at your earliest opportunity. As a future DP or director (if you go that direction), you will get a real leg up on understanding how to collaborate with Steadicam operators more effectively.