I normally went for two or three points, but if you the time limit is quite restrictive (say, 60 seconds) or if the reason both
quite uniquely applicable to the firm and also
very important to your experience as a trainee there, I think it is fine. For instance, I would not expect a recruiter at Kirkland to have an issue with you going very in depth on only one Private Equity-based motivation. However, if you applied for
Latham and only mentioned their litigation practice as a why the firm reason, that may not suffice. This is because their litigation practice, while it admittedly distinguishes
Latham from some US firms, is not as uniquely remarkable as Kirkland's PE practice; and because their litigation team is quite small compared to other departments, so it is a less central part of the firm than PE is for a firm like Kirkland.