I don't think that this is a "well known term of art" - IMHO in all the articles of last year and earlier (so before the trademark application and chatGPT proli

I don't think that this is a "well known term of art" - IMHO in all the articles of last year and earlier (so before the trademark application and chatGPT proliferation) when I've seen "GPT" used it was always in reference to one of the specific OpenAI models, not to something else.