Well, when I was working in the field it was common for gensets to be specified for 50 or 60Hz and easy for operators to change the output to suit, from one application to another. Any engine that couldn't cope with a slight overspeed to take it up to a 60Hz output was a pile of scrap in the first place and most certainly deserved no place in a genset maker's line-up.
What would happen from time to time was that a customer would specify a particular engine - like a Cummins, Gardner or Blackstone and we would supply it, while maybe having slight misgivings about it. There were favourite engines for certain customers and some of them might not have been up to the demands placed on them. In general though, we certainly had no problems with 60Hz sets popping their clogs early.
In the very early days of the North Sea oilfields it's possible the situation he described did happen, but that was before my time in it and I can't say for sure. Even then, the UK genset industry wasn't any stranger to the customers' need for a 60Hz set.
Aggreko did well by undercutting the competition, aggressive selling and offering terms and deals the others didnt, wouldn't or couldn't. Once Aggreko got to a certain size they were able to buy in bulk that the others couldn't (many smaller UK makers didn't have the turnover or spare cash to buy in and were often hampered by management that were half-dead).
That's all fine - just business and many of the other makers were asleep on their feet, thus allowing Aggreko to move in.
Doesn't change my opinion of them, though.