A good habit to practice is to see how far you can go reconciling apparent contradictions with charitable interpretation. I think in this case, I can see "brand loyalty" on a continuum ranging from "feels good about product" to "so completely loyal that lock-in would be redundant". The furthest extreme would produce an effective contradiction, but anything short of that can make sense of the term while leaving space to understand lock in as a rational, or at-least non-contradictory action.

I think that can backfire spectacularly, as we're seeing with Synology, but I suspect that a non-trivial amount of the time, it simply happens and works, no revolt is staged, and profits flow (for better or worse).

The example coming to my mind right how is Pitney Bowes, which sells big envelope stamping and sealing machines. They sell a proprietary sealing fluid (wtf) that, as far as I can tell, is water with blue food coloring. And a costly proprietary red ink cartridge for stamping. But people sign the contracts and the world keeps on keeping on.