The primary intuition driving the response that companies should boycott illiberal regimes has three flaws.
First, in a free market of money and information, a sufficiently strong boycott can have severe repercussions for the offender: consumers switch to a known competing service because. There is a problem extending this notion to an (empowering and less surveilling) company boycotting an illiberal regime; from the hypothesis I outline above, a competing service offers less empowerment or more surveillance and regulation, which in effect helps the entity being boycotted, the state; and also because of the hegemonic control of information, the entity being boycotted, the state, is unlikely to see criticism from something so minor as a company not doing business in it.
Second, one argument in favor of boycott is by analogy of economic sanctions. It puts pressure on the sanctioned company. I have to say that this is true to an extent. Companies supplying goods important to national security like oil and arms can exert influence on countries. But one does not think that Apple is critical to the national security of China: everything except for the more empowering and less surveilling services provided by Apple is provided by competing services in China. Perhaps one argues that the more empowering and less surveilling practices makes life more tolerable in the illiberal regime. In that case, I do not see the problem either: many think that Twitter and Facebook do democracy and liberalism a service because they offer empowerment and a less surveilled platform in illiberal regimes.
Finally, there is the question of where the line has to be drawn to be moral. Just as one argues that companies are immoral to participate in the economy of an illiberal regime, one also gets the argument that companies are immoral to participate in the economy of a liberal regime with illiberal elements, countries like the US where monied interests have outsized influence in its politics. It is on the onus of those arguing for boycott to provide a distinction for why doing business in the US in industries heavily shaped by lobbied interests is not immoral but doing business in China is, but thus far the current reasons I have heard being expressed for boycotting illiberal regimes do not work; one, of putting pressure on countries is also an argument for boycotting the US, and likewise for the other, for "refusing to stain one's hands" in participating in illiberal processes. By that dime, it would be immoral to receive federal subsidies for one's business that one thinks does the nation a disservice. For the two reasons I have put before this point, I argue that line drawn is not one between liberal and illiberal regimes, but whether or not a company is providing a more empowering and less surveilled experience to people living under any regime.
Of course, under a sufficiently liberal regime, and in certain contexts, empowerment and surveillance can be tradeoffs: the presence of police surveillance empowers one to go outdoors with less fear of harm being done to themselves, but this is not relevant to the argument at hand.
Unless these flaws are addressed, one is left with the case of Twitter and Facebook in illiberal regimes: they should be appreciated for their empowering and less surveilled services in illiberal regimes, rather than criticized for doing business in those regions.
Thus, if what you say is true, that Apple provides a less surveilled experience, and if my argument is true, then Apple is doing democratic preconditions and liberalism a net benefit in China. I believe the same for Dragonfly by Google, if it provides a much better search experience for Chinese consumers with not significantly more censorship than other search providers in China. Of course, Apple and Google would not be wise to make this argument publicly, for doing so would paint a bright red target on their backs.