I AB in stamps and magic all the time. I never been frozen for the refresh rates and haggle rates I use. Like you mentioned before, I put my auto bought stuff in my gallery or sdb and let it sit there for a week or so before trying to sell it. Idk if that actually helps but it makes me feel a bit safer doing so.
Also, habit is something else they might look at. Since I do stamps and magic all the time its not unreasonable for me to get faster at restocking in those shops. So going from 1600-1900ms to 1100-1200ms over a course of like a month isn't out of the question and might make you look legit.