I think that you are running into two hardware limitations.
I think that the MicroBrute gate length function only divides/multiplies based on midi or internal clock. I agree that it would be radical to have this also be possible with the incoming gate, but I'm not sure if this would be possible even with a software update. It is also a bummer because you can't sync/divide the LFO when synced to a trigger.
The reason that the MB sequence is running at half-tempo to the Volca Beats is because the Volcas (and monotribe) send one gate for every two steps. So, it is only sending 8 steps to the MB. I don't get why Korg did this with the Volcas, because it makes syncing with other gear a pain.
I found a couple workarounds for this(depending on what other gear you may have around).
At first I would make the Volca Keys my master clock and have it run double the tempo I wanted. Split the sync out of that, sending one cable to the MB and the other to a monotribe. The monotribe has a clock dividing setting that I'd turn on and then send the (now half tempo) sync signal to the Volca Beats. This would put the two in sync, but is obviously kind of ridiculous. It also left me still unable to sync the LFO.
I ultimately ended up adding midi-out to my Volca Beats. It was pretty simple. The only hard part is fitting the midi jack into the case. It wound up costing less than $5(just a midi jack and wire/solider). I wound up boring the hole with a pocket knife, which, surprisingly, gave clean results.
You could also use something else as a midi master clock and send midi to the beats and MB from there. But that can still be a pain because neither instruments have midi-out or through (unless you mod your beats
).
TDLR: midi syncing the MB will give you more flexibility, and it is more than likely a hardware limitation that makes the advanced timing options unavailable when syncing via gate.
