I do not see how that would work. If the turbos were blown, it should have been smoking before the install as well. The ypipe would not change that.
The stock ypipe is not that restrictive that it would stop smoke from blown turbo seals from being seen.
I have never heard of turbos going bad just from reinstallation after a short time unless some foreign object had been introduced to the turbo like dirt in the oil or something.
I think he just forgot to tighten something down. Be it an oil line, water line, or something on the exhaust side of the turbo. That is why I asked what the smoke smells like...
The description given is a little vague. I will wait until he responds to my questions before assuming anything further.