Would it be complicated? Yes. Do we want to support it anyway? Also yes.
Under-the-hood, transition timelines remove the timeline playback position from the timeline, and puts it back in a different place. This is true even if the transition timeline has source and destination regions that stretch the full length of the transition timeline. Because of this, a transition timeline makes the timeline playback position leave the instruments at the start of the transition timeline and enter the instruments at the end of the transition timeline, even if those instruments are technically one and the same - and so those instruments are untriggered and retriggered, just as if the timeline playback position had left and reentered them in a more conventional way.
We do want to fix this, but doing so will require some major redesign and rewriting of the relevant code, so it’ll most likely be quite some time before we’re ready to release it.
In the mean time, it’s often possible to work around the re-triggering limitation of transition timelines by not using them, and instead using a transition marker to jump to a distant section of the timeline, then using another transition marker to jump to the intended destination.