Might depend on exactly how you selected those plans and applied them to the calendar. That looks like you used Plan Builder, and then possibly swapped out Sweet Spot Base with Polarized while in the Plan Builder process?
As posted above, there are just two distinct Base or Build phases in the current POL setup for TR when viewed in their normal pages. Importantly, there is no “automatic” way to select/apply POL plans in Plan Builder.
It’s necessary to swap them to POL in the Plan Builder process. As such, I am guessing that process leaves some artifacts from what is the normal Sweet Spot Base I & Sweet Spot Base II plan phases (6 weeks each in most cases).
You can see that “Base Phase 1” is present in the example linked above, and I expect that is what you are seeing. It’s may well be that you are getting two “POL Base” phases, but that is not their typical approach external to the Plan Builder alteration covered.