I'm not arguing whether they will be constrained (initially) as to how many Bolts they can build due to the capacity of available battery factories. My point was that GM's route to the cost reductions necessary to hit $30k may simply be a different route than the one Tesla is taking. Even if GM only sells 10k Bolts per year, they can still leverage their efficiencies of scale due to their overall car business and shared parts and systems.
In short, Tesla can get to $35k largely on the back of cost reductions by investing in a massive battery plant. GM can likely get there by smaller cost advantages spread across thousands of parts (tires, bolts, paint, etc.) that their size gives them, plus the ability to reuse systems that have already been engineered for other cars in their line thus saving on design costs, plus the efficiencies of their existing massive manufacturing plants.
Yes, GM may be constrained to how many cars they can assemble because of battery availability, but that doesn't mean they don't have a feasible way to get to the target price.
Yes Tesla may be better poised to grow their EV sales than GM, but that remains to be seen due in no small part to the unfortunate impact of the various car dealer lobbyist groups that are hampering Tesla's ability to sell direct in the US. At least GM has a problem that can be solved in a straightforward manner (manufacturing investment). Tesla has to "invest" in lobbyist with a high risk of return on that investment.