That's one of the reasons Logitech is moving to Logi Bolt, which is supposed to be very similar to BLE (but with a separate receiver). I'd be really interested to know if it's also as secure as BLE.
One hint may be that on my Macbook my Logitech mouse appears to have a higher latency (feeling more "spongy") when connected via Bluetooth instead of via the dongle.
Putting a more complete Bluetooth host into their dongle would just change the edges of where it is incompatible with normal Bluetooth usage.
I've heard elsewhere Logitech devices are laggy on bluetooth. Why isn't this an issue for Apple and other manf?
I've moved from mech keyboards with O-ringed MX blues to pretty much using the Apple magic keyboard and trackpad anytime I'm at the desk. Sometimes I still reach for the clicky-claky, but integrated Touch-ID is so useful I've taken a liking to using the Apple magic keyboard (with touch id) and grown accustomed to the feel.
This is why I like their G series mice, even though I'm not a gamer. You can configure them, and they'll remember the settings on their on-board memory. They're also supported by Piper on Linux, so you never have to touch the crappy Logitech software.
I also have one of their trackballs, and it's a pain having to make sure the software runs so that the sensitivity is the correct one. It does Unifying and BT, and I've actually been impressed with how well the latter works. I don't feel any difference between that and the Unifying dongle, be it on a current-gen Linux PC or on an old MBP.
I wonder whether this is but people just don't notice because they can't directly compare.