That's the case for all bluetooth headphones. The reason is that when microphones are enabled, the codec gets downgraded to some crappy one (presumably to free up bandwidth because there are two audio streams?).
The issue isn't really bandwidth - it's about the host and device agreeing on a suitable codec.
On a Mac, my Sony headphones will fall back to the SBC codec if the mic is active. Fine for voice, but music/video/gaming sounds terrible. On Android, however, they will negotiate bi-directional AptX or some similar modern codec, so the quality is much better.
Indeed, however the AptX family has other codecs that support even better quality (AptX Lossless) and lower latency as well as adaptive bitrates, so modern AptX support is still better (hence almost as good)
On a Mac, my Sony headphones will fall back to the SBC codec if the mic is active. Fine for voice, but music/video/gaming sounds terrible. On Android, however, they will negotiate bi-directional AptX or some similar modern codec, so the quality is much better.