Lync.exe failing MFA

Thijs Lecomte that kind of makes sense.  Looking at the S4B in the task manager the running the process for S4B appears to be Lync.exe

However you say S4B supports modern auth but when i look at AzureAD logs it fails MFA as non interactive.  The entry says "User did not pass the MFA challenge (non interactive)."

So based on this I would expect S4B to not work yet it does.  Kind of contradictory.