I'm afraid I agree with Niki mate. 4-5 threads is not sufficient, and titanium being way harder than aluminium, they will just pull right out. Were the threads in the chain cover in good shape before you took it to R Tech? Do you suspect they over tightened them and they then pulled out under the load or something? These things are always your word against their's unfortunately.
The thing with pressure....think of it as resistance. Oil pumps, turbos, fuel pumps, meth pumps etc...... none of them create pressure. They create flow. Pressure is the resistance to flow, and it's that 'resistance' which brings Newton's third law into the equation, which is: "For every action, there is an equal and opposite reaction". So when Niki commands and extra 55 bar of pressure from the pump (that's 800psi of additional resistance!!), that is a LOT of additional force on the bolts.
Also remember that VW designed the pump mounting hardware to sustain 110 bar, max. When you push things beyond their design brief, you're on borrowed time.
What I don't agree with, if it's true, is how you were treated as a customer. I don't know the guy, but he has a good reputation and I can't imagine him swearing at you down the phone unless he was provoked? Professional suicide!
Anyway, get yourself a new chain cover and move on mate. Bin that silly sensor cover, I hate those stupid, ugly, pointless things