You surely don't need frontier models for any job that isn't going to replace a human. If the human is still in the loop, just use a model the human can work with. It can be quite small. You could even be running Qwen 3.8 27B for each developer and it would be fine, and you are in control of your own destiny and can make more progressive judgements about things.
I don't really understand how the AI world has caused so much black-and-white thinking to come about. You are not under mortal threat if you don't use the latest models. This is just FUD. You still have people with brains and you might get a better result over the longer term if you use AI to assist them in their choices rather than make them sit there and hit return.
But you can't trust any LLM, or any output from any LLM. You need to protect against stuff like this regardless. They could all do it, and quite accidentally. Even an LLM you trained yourself could do this to you, based on the training data and based on RAG.
But if you want to avoid the specific case we are talking about where your inference provider sees everything you do, and ignores your preferences, then running someone's LLM on your own inference is the only way forward.