The API is compatible, and even if it weren't, it wouldn't matter anyway; everybody has been writing OpenAI API-compatible proxies, including Google, for months now. The only thing that matters is availability, throughput, cost per token (Google is ahead of everyone here: Vertex API is insanely cheap for what it does, Batch API at 50% discount, Prompt Caching at 75%, fully multimodal, better performance in multilingual tasks so actually useful outside the U.S. etc etc etc)
