If they provide a compelling product offering, and the people understand what's available where, and choose to use it, then I guess that can be called vendor lock-in. But it's hardly nefarious.
It is nefarious when you build up your entire product for years, spamming it everywhere as "node but better", yell "it's so open source too!" on every roof, only to sneakily slide in lock-in features, it's worse than being nefarious. You most likely had this plan in mind all along, and actively lied to get there.
What's stopping you sticking with Deno CLI, using it for free forever, and completely ignoring anything related to Deno Deploy?
In this relationship of 3 years and counting, they are the positive contributor because they give you something useful for free and you presumably haven't given them anything.
Watch as the same happens with Bun.