I see it as being less about selling direct to consumers and more about building an EV brand with a strong service story. Right now, there is a perception that Tesla ships cars with superior technology, offers a superior charging network, but against that consumers feel Tesla has poor build quality and problems servicing its vehicles.
(This may be all or only partially true, but from a marketing perspective, what matters is whether customers perceive that these things are true, and the claim here is that they do.)
GM has to play catch-up with tech, and is doing its best with stuff like Super-cruise: https://www.gmc.com/connectivity-technology/super-cruise
But until Tesla gets its quality and service act together, brands with dealership networks like GM can differentiate themselves with their dealer network, which is also a service network... Provided the dealers invest in the tech and training to sell and service EVs.
Differentiating their products with "You can get it serviced quickly at your local Buick dealership" is not going to work if there's an asterisk and fine print that says "participating dealers only." So they're getting rid of the dealers who undercut an important part of their value proposition.
Will it work? :shrug: But this appears to be what they are attempting to do by dropping dealers who won't service EVs.
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Elsewhere, Volvo is trying to have it both ways! Their Polestar brand is sold DTC, but serviced at Volvo dealerships. That avoids the negative perception of buying from dealers who add on ridiculous charges or markups, but allows them to promise Polestar buyers that service is readily available.
TL;DR
Maybe that's exactly what GM does not want to happen with Cadillac and Buick EVs.
I'm reminded of a certain idiom about a thing you can't polish.
Is this part of a plan to shrink footprint or transition to DTC?