So for instance, let's assume (completely made up %'s; replace them with what you feel is accurate, IMO it depends on the person and their base athleticism/talent, along with where they are in the training), that the ideal way to become better at BJJ is to spend 50% conditioning, 50% learning technique/drilling/sparring. For the sake of even numbers, you train BJJ like a full time job-40 hours per week. Now let's assume you supplement that time with yoga. If you're using it as a conditioning tool, it becomes part of the conditioning aspect. Now a small portion of time for any conditioning is learning how to do that conditioning. Let's say that, after a few months of doing yoga, 90% of yoga is improving flexibility, core stabilization, whatever else, and the other 10% is learning new positions/improving how you do position. And over time that will decrease. So you spend half your conditioning time doing yoga-that's 10 hours a week, but 9/10 hours are directly improving your athleticism in a way that helps your BJJ. That would be using yoga as conditioning.
Let's take the same activities, BJJ and yoga. Now you're treating yoga and BJJ as two separate activities you enjoy. So you spend an equal time doing both of them. Or even, let's assume you like BJJ more so you spend 25 hours BJJ and 15 hours yoga. Now, instead of taking specifically from the conditioning time, which for BJJ should involve core and flexibility as well, you are taking away 7.5 hours from that, and 7.5 hours from technique/drilling/sparring. So your ratio is slightly off (from 20-20 to 27.5-12.5), making you less efficient-you'll be more athletic than you otherwise would be, but you'll learn/develop BJJ skills less quickly.
Now let's take a different activity-basketball. I'm using that simply because I know very little about breakdancing so can't really use it as an example. For basketball you need to have good hand-eye coordination, cardio, quick movements, and be able to use short bursts of energy while also recovering your energy/stamina at different points while still remaining active. Pretty similar, sans flexibility (which is also important but much less so), to the conditioning that you need for BJJ. There's also a mental part where you have to be focusing and thinking on a larger picture while you're engaged physically, also similar to BJJ. But to me it would only fit as a complementary activity.
For basketball you have specific skills that you need to learn - how to shoot, how to pass, pick and roles, observing your teammates and finding holes in the floor, and feints. No matter how good your conditioning is, you won't be good if you can't shoot, or spend the entire time ignoring your teammates and staying guarded. So let's say you decide to replace 10 hours of your conditioning with basketball, instead of with yoga. Now you've got to spend a decent amount of that time doing partner drills, or even if you're just training for one-on-one b-ball, you have to spend a lot of that time working on your shot. Which still does condition your cardio and footwork a bit, but less so. So instead of wasting 1 hour a week, you're now wasting 5.
Not the biggest thing, but let's say that you do the same split from earlier where you're training them both as complementary rather than one as a tool for the other, with the same 25/15 split. So the split is now listed as: 12.5 hours BJJ conditioning, 12.5 hours BJJ tech, 7.5 hours basketball conditioning, and 7.5 hours basketball tech. Some of the conditioning for basketball might not be fully relevant, but I'll give the benefit of the doubt and say it's so complementary that all of it fits. That's now 20 hours BJJ conditioning, and 12.5 hours BJJ tech. So now you're still learning less in the skills/tech department, with no change to your conditioning.
And again, those numbers and ratio are subject to change, the ones I used was mostly for ease of illustrating the concept.
