It is very odd that the two boreholes didn't show the existence of rock. That is after all the job of the slab engineer.
Definately get out to site and try to see the rock for yourself.
Question everything.
If it looks like a duck and quacks like a duck.... maybe it is a duck.
Thanks mate. That's what I thought as well....
I did go to the site, I could see some rocks at the start of the site but not that massive though