Fair enough, when looking at the academic origin and defintions; but googling a bit and looking at articles like https://medium.com/@.RT/total-n00bs-guide-to-bi

Fair enough, when looking at the academic origin and defintions; but googling a bit and looking at articles like https://medium.com/@.RT/total-n00bs-guide-to-big-o-big-%CF%89-big-%CE%B8-aa259ae8a1c2 https://medium.com/@.RT/total-n00bs-guide-to-big-o-big-%CF%8... (under 'The Big Caveat', third paragraph), I feel validated in my assertion that your 'Big theta' is what is in practice and colloquially is known as 'Big O', and is also what this article is talking about. (But I'll admit that I had mostly forgotten about this distinction, and certainly couldn't tell which one is which without looking it up)