As someone else pointed out it is not actually bandwidth problem. Reason behind this is that high quality audio streaming profile A2DP is one-way only and once mic is needed, profile is changed to bidirectional but low quality HSP. My workaround for conference calls is to use my MacBook's internal microphone instead of one of my Bluetooth headset.
I suspect that the underlying reason that the profile switch happens, though, is because of bandwidth limits. That’s what Sennheiser is telling their customers, at least.
The real answer may be more subtle than that. Maybe there is just enough bandwidth, but using it would have an adverse effect on latency, which bidirectional use cases are more sensitive to.
Either way, the profiles were designed within constraints. They’re not arbitrary.
