Lots wrong as noted, and I would look carefully at the entire tail, if not airplane, for other plan “deviations”.
The good news, he can now do the HS SB and not feel like you’re taking apart a perfectly good HS. Consider this an opportunity.
Good catch on the inspection but this area is one that has been historically the worst for build error.
Most of the time it’s edge distance issues, but have seen this “floating” HS Spar issue before, on airplanes that have flow for many hours. Scary, but also a testimonial for how robust this design is when properly executed.
I would check this area before I bought any RV, and certainly that machine is grounded!