It's basically impossible that it's a random irrelevant detail, I'd say any such detail is fair to share.
For example, if every member of this group was Indian American I'd consider that a fair detail to note, the chances of that happening at random are minuscule, yet that's orders of magnitude more probable than all of them being trans for no reason.
> the chances of that happening at random are minuscule
No it's not, what? People tend to hang out with people similar to them. Most gangs are racially or ethnically homogenous. That's fairly normal.
In fact, there are commonly Indian-origin gangs in Canada (I haven't heard of it in the US, but the US has much higher-income immigrants from India overall)
For example, if every member of this group was Indian American I'd consider that a fair detail to note, the chances of that happening at random are minuscule, yet that's orders of magnitude more probable than all of them being trans for no reason.