Let's not get this twisted, Larian can decide if Shar's iconography is well known or not in their game. FR isn't a real place, every 'fact' about it is subject to change, if the writer finds it inconvenient. So the onus is on Larian to tell us whether Shar commandos go around wearing such, or if Onyx is somehow treyf
They could do that, but consistency is important in stories, fictional or not, and changing things greatly or often is likely to confuse fans and even those who are new to a series. Retcons, reboots, etc. are tools that should be used very sparingly, and I don't think that it's a wise use of those tools to potentially erase or change huge portions of Shar's history in the setting with no in-universe justification just so that Shar's followers can go around with their signature appearance without being criticized or attacked.