Training a XENO unit does not initiate Dormant Construct survey on the same body.
My HW (non-Sol start) has an Ancient Construct, which was dormant at game start.
After some years, I finally constructed a XENO ground unit.
I left the unit on the HW and waited for it to survey the construct.
And I waited.
And waited.
And waited.
After 9+ years of no results, I loaded the unit on a transport, and immediately unloaded the unit back to the surface.
Five months later, the construct was reported as surveyed.
So, it seems like the code only starts calculating construct survey chances after a XENO unit is unloaded onto the body.
Training a unit locally does not seem to trigger it.