Storm - yes sport fighting is not real fighting but it is a damn site closer than form styles are. As you would probably know there are many gradients of sports fighting & the more open (& intense) the sport combat then the more likely it is going to be better for reality eg. light kick, clash or even koshiki is not the same as muay thai or mma comps (even at the amateur levels). As for RBSD - they teach what sports guys usually don't teach which is situational awareness & appropriate action. Really useful but unless they compete they lack the edge required to really apply the methods (internal pressure sparing is great but taking that to open hyper competitive sports match just makes it better).
So XYLH? Not really a sports style & not a RBSD. It could easily be but the instructors who have gone this path mix it up with sanda, swaijiow, techniques + reaction drills. So it's kind of XYLH with a more open view on testing it.
But what is it that XYLH does add to sports styles or realism? What it does is build really great pliable strength which can be carried throughout life (a great definition for health imo). This same strength can work really well when applied because it focuses in on applying power using muscles that most people don't get.
Should you cross train XYLH? I would say no due to your time limits & not for the initial stages. The only time I would recommend this is because there is a limited window of time to learn from someone (ie give me a brain dump before I leave) or they already have a real solid foundation & strength structure. That said after a couple of years of doing the drills every XYLH instructor I have met would recommend cross training.
Why not in the early stages? Because XYLH methods take time & energy to retune the body.
XYLH in its original form did not have many forms. Why? Because the focus was not on learning more moves but on growing strength & power. Not in providing a student 100s of different forms or moves or tactics. Mixing bagua, hsing-i, taichi or even learning in the 1st month 10 different xylh forms does not change the fact that the goal is not about strengthening the body.
This transformation is not magical but is just good old body weight conditioning. Take for example xylh chicken. I could show someone all the forms in less than 10 minutes & then create 100s of variations of applied chicken forms for them to learn. But this misses the point that the legs needs to be so conditioned that they can be held at this position plus that they must move easily & comfortably ... fast!
What does it do? Done for an extended period of time a person should easily be able to squat x 5 (and more) their body weight yet have explosive power. When achieved then imagine how much more powerful a thrust kick to the stomach would be?
This is the goal of the conditioning & the objective of XYLH for all the major body parts (legs, waist, shoulders, arms etc.).
With this foundation in place the goal then is to continue the growth & conditioning while learning to apply it. After a couple of years of "basics" cross training is the norm for the XYLH guys if they want to develop more but some tend to just keep doing the exercises because they really help in life & they are not fixated on fighting.