Users of the plugin already have a trust and consumption relationship with Automattic for the core.
It's more like mcdonalds replacing Coke with McCola with your mcdonalds meal - you were already trusting mcdonalds for the food. But even that is a stretch since both are GPL2 and there's no current sign the plugin Automattic provide differs from the WP Engine one.
GPL is on both sides, nothing stops WP Engine doing the same and providing their own flavour of core with their plugin, if that's what people want. Of course that costs more than private equity just using Automattic's core for free.
I feel like the dodgy part isn’t the forking. Any open source project can be forked at any time by anyone. The dodgy part is them automatically switching existing users to their fork.
To use your McDonald’s analogy, it’s like specifically ordering a Coke and McD’s secretly switching it to a McCoke without you noticing.
As I wrote elsewhere, this is no different from a project deciding to incorporate a third party's functionality into the core. Either way whoever provides the plugin, you trust the provider to provide the core, if you now think they are going to do bad things, there is nothing they can do in the plugin that they couldn't do in the core without all this drama.
It seems the "perceptual framing" that is being engineered about this, that Automattic and its leader should be cancelled, is not about technical issues.
