Well, i talk from personal experience. It were times before finding this forum, i'd brought my cheap quartz breitling chronomt rep to ad and bought a gen strap, they put it on. I dont know if they noticed its a rep but i had no problems.
But i also dont suggest bringing a rep to AD, just go in and buy the strap alone (if they say they cant do it without seeing the watch and you say " you wanna sell the strap or not?here is the money" ..btw dont bring a photo of your watch lol , just tell them the measurements