You're reading way too much into this. Rivian has been trying to give R1 shop access to everyone at some point in the order process. It's a benefit, for people who are flexible in their configuration and care more about getting something sooner than getting their exact configuration. I got access to the shop three months before my delivery window, but I waited and my original configuration was delivered a few weeks BEFORE my delivery window.
Access to the shop doesn't mean you're being delayed. It also doesn't mean you'll get it sooner by choosing out of the shop. BTW, I haven't heard of any R1S being in the shop yet. They are still working on fulfilling the Launch Edition R1S, and they have locked in the configuration for most R1S orders expected to be delivered in the next six months. The shop would be a way to get something different after you locked in, but as I said no R1S have been in the shop yet.
If you have a 2019 R1S LE then that's what they're shipping right about now, so you seem to be right on track to get your 8 steps in Feb/Mar. If you have an Adventure, they're not shipping those yet, but I haven't heard of any Adventure people being given a window as soon as Feb/Mar either ... Rivian is also batching orders, most notably right now for interior color, so your build could be waiting for the right batch. I think OC is up next - they haven't been shipping R1S with OC, but if past behavior holds then once they start most of the interiors are going to be OC.