>I have heard many times that the traditional car companies are heavily outsourced aside from the drivetrain.

It's true, but I don't think it matters. Traditional automakers rely on suppliers for all kinds of parts on cars: headlights, wipers, tires, glass, airbags, and many electronic modules (auto-dimming mirrors, blind-spot radars, etc.). However they do tend to always keep the body/chassis and the drivetrain in-house (sometimes they'll outsource the transmission, like to ZF).

I don't see how this would affect them moving to EVs. Going from ICE to EV means two giant changes: the chassis (to make room for an entirely different layout, esp. because of the batteries), and the drivetrain. Well, the automaker controls both of those. All those other things, like glass, headlights, electronic safety add-ons, etc., are going to be the same either way. You don't need a different blind-spot monitoring system or windshield wipers or tires just because the drivetrain is electric.

Moving to EVs, they either outsource the drivetrain (as the comment I replied to was suggesting, and as GM is doing with the Bolt) or start doing EV drivetrains in house. Either way, they lose the advantage of their long experience with ICE drivetrains.

Sure, but they don't lose their advantages with chassis design (crashworthy design and testing is hard), manufacturing at scale, logistics, etc. It's not like there's a ton of serious EV competitors out there anyway; there's only Tesla (which can't manufacture at huge volumes), and a few other traditional automakers that have also dipped their toes into EV production.

The Bolt uses a drivetrain built by LG.

Right, so what is GM bringing to the table there? If the Bolt were to somehow become a best seller, how much benefit would GM see?

Lots of design knowledge around vehicles, both from an aesthetic standpoint and in a number of other subsystems. But the bigger point is actually that GM, Ford, and the other major car manufacturers are really giant project management and logistic organizations. They are far from perfect corporations, but don't undersell what they do.