First off a few questions.
Did the car run fine before you took it to the mechanic?
Does the engine have a miss as well as the noise? Listen to the tail pipe for a sucking noise while idling.
The mechanic was correct in asking you to replace the parts during the repair. If the water pump was to fail at later date you would be changing the timing belt as well again. That part he got right.
The repair procedure and his mechanical skills is what I question.
My take:
It sounds like they miss timed the engine when they installed the timing belt and started the vehicle. On certain engines this can cause the valve to hit the top of the piston damaging the valve.
What I mean by miss timed is that the belt could have been one to two teeth off when it was installed. Once the mechanic started the engine it would have instantly damaged the valve.
Again I am not sure on this year of engine. Your dealer would know though. Also since your car is going to the dealer ask them to chk for the timing belt being properly installed and timed. Request pictures if not. Now this may not be to easy identify. The mechanic could have realized that he fucked up and then went back and properly timed the engine to cover his mistake. Hoping that somehow it would fix the issue. I am just giving possible scenarios here. You will know more once the engine is torn down again.
I have seen this happen many a times to customers. I used to fix idiots mistakes all the time. Had the mechanic taken the proper time to rotate the engine by hand after installation and had he rechecked the alignment then this could have been avoided if that is the issue now.
Valves just don't bend on there own. They have to strike something from mechanical failure or improper repair procedure.
If the valve is bent you are looking at a very costly repair well over 1,000 dollars I would imagine. The cylinder head is likely damage as well. The valve guide and seat will need machined or replaced. The cylinder head could be damaged or cracked as well from the bent valve. If that is the case then the repair will be even more.
Oil is not the issue here. Nor is it a recall issue.This guy sounds like an idiot and is not being truthful. I don't care what oil you use as long as it meets the manufacturers requirement and you service it at the proper interval your engine will last for well over 100,000+ miles.
You have been had by a shade tree mechanic would be my best guess.
When it comes to automotive repair; cheaper is not always better. Always ask for an ASE certified mechanic. If the shop does not have one move on to the next.
Hope this helps.