Nice find, yes that's a bug and I'm experiencing it too. I hadn't touched that flag but it didn't matter if it was set to enabled or disabled, still Bing would give me this message and prevent me from changing safesearch settings:
"We've set SafeSearch to strict because your browser communicated your preference for a safe web browsing experience."
Version 78.0.274.0 (Official build) canary (64-bit)
@_shellprompt1515 I'm also experiencing the same problem in both a normal window and in an InPrivate mode window. It seems to only affect Bing. Google and DuckDuckGo seem to work fine. The problem does not exist using Bing on the legacy Edge browser.