What is wrong with a manager who is considering bringing you onto their team wanting to know about your past performance at the company? I bet that happens at EVERY company. It certainly did at Microsoft.
Because software development is not the 100 metres. You could spend weeks on a particularly elusive and obscure bug and change one line of code. While you were doing that, your colleague built 2 new 'oh wow' features, banging out hundreds of lines. There is no standardised measurement for 'performance' that can rank those two achievements objectively, so to assess performance, it comes down to the subjective opinion, motivations and political goals of the 'assessor'.
More to the point, if the subjective performance metric rewards the latter and punishes the former, the net result is more features AND more bugs.
Of course, the manager is going to want to know. People would rather have information than not have it, even if it's wildly inappropriate.
Microsoft was destroyed by stack-ranking and the global visibility of political-success review (I mean, "performance review") history. Are you seriously trying to use Microsoft to make a case?
